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{{Short description|Sources of water that are potentially useful for humans}}
]
{{About|all types of waters that are of potential use to humans|a naturally occurring type of water resource that humans use a lot|fresh water}}{{Pie chart|thumb=right|caption=Distribution of freshwater resources by type<ref>{{Cite web |title=Strains on freshwater resources |url=https://datatopics.worldbank.org/sdgatlas/goal-6-clean-water-and-sanitation?lang=en#c4s1 |access-date=2024-05-19 |website=Atlas of Sustainable Development Goals 2023 |language=en}}</ref>|other=|label1=]|value1=69|color1=#AFEEEE|label2=]|value2=30|color2=#1E90FF|label3=Other Freshwater (e.g., Soil Moisture)|value3=0.7|color3=#ef8e39|label4=Directly Accessible Water|value4=0.3|color4=#000080}}'''Water resources''' are ]s of ] that are potentially useful for humans, for example as a source of drinking ] or ] water. These resources can be either ] from natural sources, or water produced artificially from other sources, such as from ] (]) or ] water (]). 97% of the water on Earth is ] and only three percent is ]; slightly over two-thirds of this is frozen in ]s and ] ]s.<ref name="USGS dist">{{cite web|url=http://ga.water.usgs.gov/edu/waterdistribution.html|title=Earth's water distribution|publisher=United States Geological Survey|access-date=2009-05-13}}</ref> The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air.<ref>{{cite web | title=Scientific Facts on Water: State of the Resource| publisher=GreenFacts Website | access-date=2008-01-31 | url= http://www.greenfacts.org/en/water-resources/index.htm#2}}</ref> Natural sources of ] include ], under river flow, ] and ]. People use water resources for ], ] and ] activities.


Water resources are under threat from multiple issues. There is ], ], ] and ]. Fresh water is in principle a ]. However, the world's supply of ] is steadily decreasing. Groundwater depletion (or ]) is occurring for example in Asia, South America and North America.
'''Water resources ''' are sources of ] that are useful or potentially useful to ]s. Uses of water include ], ], ], ] and ] activities. Virtually all of these human uses require ].


{{TOC limit|3}}
97% of water on the Earth is salt water, and only 3% is fresh water of which slightly over two thirds is frozen in ]s and ] ]s.<ref name="USGS dist">{{cite web|url=http://ga.water.usgs.gov/edu/waterdistribution.html|title=Earth's water distribution|publisher=United States Geological Survey|accessdate=2009-05-13}}</ref> The remaining unfrozen freshwater is mainly found as groundwater, with only a small fraction present above ground or in the air.<ref>{{cite web | title=Scientific Facts on Water: State of the Resource| publisher=GreenFacts Website | accessdate=2008-01-31 | url= http://www.greenfacts.org/en/water-resources/index.htm#2}}</ref>


== Natural sources of fresh water ==
Fresh water is a ], yet the world's supply of clean, fresh water is steadily decreasing. Water demand already ] in many parts of the world and as the ] continues to rise, so too does the water demand. Awareness of the global importance of preserving ] for ] has only recently emerged as, during the 20th century, more than half the world’s ] have been lost along with their valuable environmental services. ]-rich ] ecosystems are currently declining faster than ] or land ]s.<ref name="water"> Hoekstra, A.Y. 2006. The Global Dimension of Water Governance: Nine Reasons for Global Arrangements in Order to Cope with Local Problems. ''Value of Water Research Report Series'' No. 20 UNESCO-IHE Institute for Water Education.</ref> The framework for allocating water resources to water users (where such a framework exists) is known as ].
{{Further|Water distribution on Earth}}Natural sources of ] include ], under river flow, ] and ].


=== Surface water ===
]

==Sources of fresh water==
===Surface water===
{{Main|Surface water}} {{Main|Surface water}}
] and ] volcano in northern Chile]]
Surface water is water in a river, ] or fresh water ]. Surface water is naturally replenished by ] and naturally lost through discharge to the ], ], ] and sub-surface seepage.gay


] and ] volcano in northern Chile]]
Although the only natural input to any surface water system is precipitation within its ], the total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial ], the permeability of the ] beneath these storage bodies, the ] characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water lost.


Surface water is water in a river, ] or fresh water ]. Surface water is naturally replenished by ] and naturally lost through discharge to the ], ], ] and ]. The only natural input to any surface water system is precipitation within its ]. The total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial ], the permeability of the ] beneath these storage bodies, the ] characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water loss.
Human activities can have a large and sometimes devastating impact on these factors. Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing stream flow.


Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing the stream flow.
The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many ]s require large quantities of water in the spring, and no water at all in the winter. To supply such a farm with water, a surface water system may require a large storage capacity to collect water throughout the year and release it in a short period of time. Other users have a continuous need for water, such as a ] that requires water for cooling. To supply such a power plant with water, a surface water system only needs enough storage capacity to fill in when average stream flow is below the power plant's need.


Natural surface water can be augmented by importing surface water from another watershed through a ] or ].
Nevertheless, over the long term the average rate of precipitation within a watershed is the upper bound for average consumption of natural surface water from that watershed.


] is estimated to have the largest supply of fresh water in the world, followed by ] and ].<ref>{{cite web|url=http://www.worldwater.org/data.html |title=The World's Water 2006–2007 Tables, Pacific Institute |publisher=Worldwater.org |access-date=2009-03-12}}</ref>
Natural surface water can be augmented by importing surface water from another watershed through a ] or ]. It can also be artificially augmented from any of the other sources listed here, however in practice the quantities are negligible. Humans can also cause surface water to be "lost" (i.e. become unusable) through ].


<gallery class="center" mode="packed" heights="85px">
] is the country estimated to have the largest supply of fresh water in the world, followed by ] and ].<ref>{{cite web|url=http://www.worldwater.org/data.html |title=The World's Water 2006-2007 Tables, Pacific Institute |publisher=Worldwater.org |date= |accessdate=2009-03-12}}</ref>
Image:Sinclair Wetlands.jpg|''Panorama of a natural wetland (], New Zealand)''
</gallery>


===Under river flow=== ==== Water from glaciers ====
] runoff is considered to be surface water. The Himalayas, which are often called "The Roof of the World", contain some of the most extensive and rough high altitude areas on Earth as well as the greatest area of glaciers and permafrost outside of the poles. Ten of Asia's largest rivers flow from there, and more than a billion people's livelihoods depend on them. To complicate matters, temperatures there are rising more rapidly than the global average. In Nepal, the temperature has risen by 0.6 degrees Celsius over the last decade, whereas globally, the Earth has warmed approximately 0.7 degrees Celsius over the last hundred years.<ref> {{webarchive|url=https://web.archive.org/web/20090723050437/http://pulitzercenter.org/showproject.cfm?id=106|date=July 23, 2009}}</ref>
Throughout the course of the river, the total volume of water transported downstream will often be a combination of the visible free water flow together with a substantial contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain called the hyporheic zone. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. The hyporheic zone often forms a dynamic interface between surface water and true ground-water receiving water from the ground water when aquifers are fully charged and contributing water to ground-water when ground waters are depleted. This is especially significant in karst areas where pot-holes and underground rivers are common.


===Ground water=== === Groundwater ===
]
{{Main|ground water
{{excerpt|Groundwater|paragraphs=1-2|file=no}}
]
], a common water source in ] villages]]


==== Under river flow ====
Sub-surface water, or groundwater, is fresh water located in the ] space of soil and ]. It is also water that is flowing within ]s below the ]. Sometimes it is useful to make a distinction between sub-surface water that is closely associated with surface water and deep sub-surface water in an aquifer (sometimes called "fossil water").
Throughout the course of a river, the total volume of water transported downstream will often be a combination of the visible free water flow together with a substantial contribution flowing through rocks and sediments that underlie the river and its floodplain called the ]. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. The hyporheic zone often forms a dynamic interface between surface water and groundwater from aquifers, exchanging flow between rivers and aquifers that may be fully charged or depleted. This is especially significant in ] areas where pot-holes and underground rivers are common.


== Artificial sources of usable water ==
Sub-surface water can be thought of in the same terms as surface water: inputs, outputs and storage. The critical difference is that due to its slow rate of turnover, sub-surface water storage is generally much larger compared to inputs than it is for surface water. This difference makes it easy for humans to use sub-surface water unsustainably for a long time without severe consequences. Nevertheless, over the long term the average rate of seepage above a sub-surface water source is the upper bound for average consumption of water from that source.
There are several artificial sources of fresh water. One is ] (]). Another is ]s.<ref>{{cite journal |last1=Shafeian |first1=Nafise |last2=Ranjbar |first2=A.A. |last3=Gorji |first3=Tahereh B. |title=Progress in atmospheric water generation systems: A review |journal=Renewable and Sustainable Energy Reviews |date=June 2022 |volume=161 |pages=112325 |doi=10.1016/j.rser.2022.112325 |s2cid=247689027 |language=en}}</ref><ref>{{cite journal |last1=Jarimi |first1=Hasila |last2=Powell |first2=Richard |last3=Riffat |first3=Saffa |title=Review of sustainable methods for atmospheric water harvesting |journal=International Journal of Low-Carbon Technologies |date=18 May 2020 |volume=15 |issue=2 |pages=253–276 |doi=10.1093/ijlct/ctz072|doi-access=free }}</ref><ref>{{cite journal |last1=Raveesh |first1=G. |last2=Goyal |first2=R. |last3=Tyagi |first3=S.K. |title=Advances in atmospheric water generation technologies |journal=Energy Conversion and Management |date=July 2021 |volume=239 |pages=114226 |doi=10.1016/j.enconman.2021.114226|bibcode=2021ECM...23914226R |s2cid=236264708 }}</ref> ] is another important source. It is important to consider the economic and environmental side effects of these technologies.<ref>{{Cite journal|last1=van Vliet|first1=Michelle T H|last2=Jones|first2=Edward R|last3=Flörke|first3=Martina|last4=Franssen|first4=Wietse H P|last5=Hanasaki|first5=Naota|last6=Wada|first6=Yoshihide|last7=Yearsley|first7=John R|date=2021-02-01|title=Global water scarcity including surface water quality and expansions of clean water technologies|journal=Environmental Research Letters|volume=16|issue=2|pages=024020|bibcode=2021ERL....16b4020V|doi=10.1088/1748-9326/abbfc3|issn=1748-9326|doi-access=free}}</ref>


=== Wastewater reuse ===
The natural input to sub-surface water is seepage from surface water. The natural outputs from sub-surface water are ] and seepage to the oceans.
{{excerpt|Reclaimed water|paragraphs=1,2|file=no}} <!-- this takes the first two paragraphs of the lead of the sub-article -->


=== Desalinated water ===
If the surface water source is also subject to substantial evaporation, a sub-surface water source may become ]. This situation can occur naturally under ] bodies of water, or artificially under ] farmland. In coastal areas, human use of a sub-surface water source may cause the direction of seepage to ocean to reverse which can also cause ]. Humans can also cause sub-surface water to be "lost" (i.e. become unusable) through pollution. Humans can increase the input to a sub-surface water source by building reservoirs or detention ponds.
{{Excerpt|Desalination|paragraphs=1,2|file=no}}


=== Research into other options ===
===Desalination===
{{Main|Desalination}}
Desalination is an artificial process by which ] (generally ]) is converted to fresh water. The most common desalination processes are ] and ]. Desalination is currently expensive compared to most alternative sources of water, and only a very small fraction of total human use is satisfied by desalination. It is only economically practical for high-valued uses (such as household and industrial uses) in ] areas. The most extensive use is in the ].


]<ref name="10.1038/s41598-022-24314-2">{{cite journal |last1=Rahman |first1=Afeefa |last2=Kumar |first2=Praveen |last3=Dominguez |first3=Francina |date=6 December 2022 |title=Increasing freshwater supply to sustainably address global water security at scale |journal=Scientific Reports |language=en |volume=12 |issue=1 |pages=20262 |bibcode=2022NatSR..1220262R |doi=10.1038/s41598-022-24314-2 |issn=2045-2322 |pmc=9726751 |pmid=36473864 |doi-access=free}}
===Frozen water===
*University press release: {{cite news |title=Researchers propose new structures to harvest untapped source of freshwater |language=en |work=University of Illinois at Urbana-Champaign via techxplore.com |url=https://techxplore.com/news/2022-12-harvest-untapped-source-freshwater.html |access-date=17 January 2023}}</ref>]]
]]]
Researchers proposed air capture over oceans which would "significantly increasing freshwater through the ] over oceans" to address present and, especially, future water scarcity/insecurity.<ref>{{cite news |last1=McDonald |first1=Bob |title=Water, water, everywhere — and maybe here's how to make it drinkable |url=https://www.cbc.ca/radio/quirks/water-water-everywhere-and-maybe-here-s-how-to-make-it-drinkable-1.6703854 |access-date=17 January 2023}}</ref><ref name="10.1038/s41598-022-24314-2" />
Several schemes have been proposed to make use of ]s as a water source, however to date this has only been done for novelty purposes. Glacier runoff is considered to be surface water.


A 2021 study proposed hypothetical portable solar-powered ]. However, such ] generation may sometimes "undermine efforts to develop ]" among other problems.<ref>{{cite news |last1=Yirka |first1=Bob |title=Model suggests a billion people could get safe drinking water from hypothetical harvesting device |language=en |work=Tech Xplore |url=https://techxplore.com/news/2021-10-billion-people-safe-hypothetical-harvesting.html |access-date=15 November 2021}}</ref><ref>{{cite news |date=13 November 2021 |title=Solar-powered harvesters could produce clean water for one billion people |work=Physics World |url=https://physicsworld.com/a/solar-powered-harvesters-could-produce-clean-water-for-one-billion-people/ |access-date=15 November 2021}}</ref><ref>{{cite journal |last1=Lord |first1=Jackson |last2=Thomas |first2=Ashley |last3=Treat |first3=Neil |last4=Forkin |first4=Matthew |last5=Bain |first5=Robert |last6=Dulac |first6=Pierre |last7=Behroozi |first7=Cyrus H. |last8=Mamutov |first8=Tilek |last9=Fongheiser |first9=Jillia |last10=Kobilansky |first10=Nicole |last11=Washburn |first11=Shane |last12=Truesdell |first12=Claudia |last13=Lee |first13=Clare |last14=Schmaelzle |first14=Philipp H. |date=October 2021 |title=Global potential for harvesting drinking water from air using solar energy |journal=Nature |language=en |volume=598 |issue=7882 |pages=611–617 |bibcode=2021Natur.598..611L |doi=10.1038/s41586-021-03900-w |issn=1476-4687 |pmc=8550973 |pmid=34707305}}</ref>
The Himalayas, which are often called "The Roof of the World", contain some of the most extensive and rough high altitude areas on Earth as well as the greatest area of glaciers and permafrost outside of the poles. Ten of Asia’s largest rivers flow from there, and more than a billion people’s livelihoods depend on them. To complicate matters, temperatures are rising more rapidly here than the global average. In Nepal the temperature has risen with 0.6 degree over the last decade, whereas the global warming has been around 0.7 over the last hundred years.<ref>http://pulitzercenter.org/showproject.cfm?id=106</ref>
{{-}}


==Uses of fresh water== == Water uses ==
].]]]The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many ]s require large quantities of water in the spring, and no water at all in the winter. Other users have a continuous need for water, such as a ] that requires water for cooling. Over the long term the average rate of precipitation within a watershed is the upper bound for average consumption of natural surface water from that watershed.
Uses of fresh water can be categorized as consumptive and non-consumptive (sometimes called "renewable"). A use of water is consumptive if that water is not immediately available for another use. Losses to sub-surface seepage and evaporation are considered consumptive, as is water incorporated into a product (such as farm produce). Water that can be ] and returned as surface water, such as sewage, is generally considered non-consumptive if that water can be put to additional use.


===Agriculture and other irrigation===
===Agricultural===
{{Further|Sustainable Water and Innovative Irrigation Management}}
]]]
{{excerpt|Irrigation|paragraphs=1-3}}
It is estimated that 69% of worldwide water use is for irrigation, with 15-35% of irrigation withdrawals being unsustainable.<ref name="WBCSD Water Facts & Trends">{{cite web|url=http://www.wbcsd.org/includes/getTarget.asp?type=d&id=MTYyNTA |title=WBCSD Water Facts & Trends |date= |accessdate=2009-03-12}}</ref>


=== Industries ===
In some areas of the world irrigation is necessary to grow any crop at all, in other areas it permits more profitable crops to be grown or enhances crop yield. Various irrigation methods involve different trade-offs between crop yield, water consumption and capital cost of equipment and structures. Irrigation methods such as ] and overhead ] irrigation are usually less expensive but are also typically less efficient, because much of the water evaporates, runs off or drains below the root zone. Other irrigation methods considered to be more efficient include ], ], and some types of sprinkler systems where the sprinklers are operated near ground level. These types of systems, while more expensive, usually offer greater potential to minimize runoff, drainage and evaporation. Any system that is improperly managed can be wasteful, all methods have the potential for high efficiencies under suitable conditions, appropriate irrigation timing and management. One issue that is often insufficiently considered is salinization of sub-surface water.
{{See also|Industrial water treatment|Industrial wastewater treatment}}It is estimated that 22% of worldwide water is used in ].<ref name="WBCSD Water Facts & Trends">{{cite web |url=http://www.wbcsd.org/includes/getTarget.asp?type=d&id=MTYyNTA |title=WBCSD Water Facts & Trends |access-date=2009-03-12 |archive-date=2012-03-01 |archive-url=https://web.archive.org/web/20120301011840/http://www.wbcsd.org/includes/getTarget.asp?type=d&id=MTYyNTA |url-status=dead }}</ref> Major industrial users include ] dams, ], which use water for ], ] and ], which use water in ]es, and manufacturing plants, which use water as a ]. Water withdrawal can be very high for certain industries, but consumption is generally much lower than that of agriculture.


Water is used in ] generation. ] derives energy from the force of water flowing downhill, driving a turbine connected to a generator. This ] is a low-cost, non-polluting, renewable energy source. Significantly, hydroelectric power can also be used for ] unlike most renewable energy sources which are ]. Ultimately, the energy in a hydroelectric power plant is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes and flows downhill. ] plants also exist, which use grid electricity to pump water uphill when demand is low, and use the stored water to produce electricity when demand is high.
] is a small but growing agricultural use of water. Freshwater commercial fisheries may also be considered as agricultural uses of water, but have generally been assigned a lower priority than irrigation (see ] and ]).


Thermoelectric power plants using ] have high consumption, nearly equal to their withdrawal, as most of the withdrawn water is evaporated as part of the cooling process. The withdrawal, however, is lower than in ] systems.
As global populations grow, and as demand for food increases in a world with a fixed water supply, there are efforts underway to learn how to produce more food with less water, through improvements in irrigation<ref>{{cite web|url=http://www.fao.org/nr/water/topics_irrigation.html |title=Water Development and Management Unit - Topics - Irrigation |publisher=FAO |date= |accessdate=2009-03-12}}</ref> methods<ref>{{cite web|url=http://www.fao.org/nr/water/news/masscote.html |title=FAO Water Unit &#124; Water News: water scarcity |publisher=Fao.org |date= |accessdate=2009-03-12}}</ref> and ], agricultural ], crop types, and water monitoring.


Water is also used in many large scale industrial processes, such as thermoelectric power production, oil refining, ] production and other ] use, and ] from ]. Discharge of untreated water from industrial uses is ]. Pollution includes discharged solutes and increased water temperature (]).
===Industrial===
]]]
It is estimated that 22% of worldwide water use is industrial.<ref name="WBCSD Water Facts & Trends" /> Major industrial users include power plants, which use water for cooling or as a power source (i.e. ] plants), ] and ] refineries, which use water in chemical processes, and manufacturing plants, which use water as a solvent.


=== Drinking water and domestic use (households) ===
The portion of industrial water usage that is consumptive varies widely, but as a whole is lower than agricultural
{{Main|Water supply|Drinking water|Water footprint}}


]
Water is also used in many industrial processes and machines, such as the steam turbine and heat exchanger, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requires pure water for many applications and utilizes a variety of purification techniques both in water supply and discharge.


It is estimated that 8% of worldwide water use is for domestic purposes.<ref name="WBCSD Water Facts & Trends" /> These include ], ], ], ], cleaning, laundry and ]. Basic domestic water requirements have been estimated by ] at around 50 liters per person per day, excluding water for gardens.
===Household===
]
It is estimated that 8% of worldwide water use is for household purposes.<ref name="WBCSD Water Facts &
Trends"></ref> These include ], ], ], sanitation, and ]. Basic household water requirements have been estimated by ] at around 50 liters per person per day, excluding water for gardens.
Drinking water is water that is of sufficiently high quality so that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard even though only a very small proportion is actually consumed or used in food preparation.


Drinking water is water that is of sufficiently high quality so that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries, the water supplied to domestic, commerce and industry is all of drinking water standard even though only a very small proportion is actually consumed or used in food preparation.
===Recreation===
]
]al water use is usually a very small but growing percentage of total water use. Recreational water use is mostly tied to reservoirs. If a reservoir is kept fuller than it would otherwise be for recreation, then the water retained could be categorized as recreational usage. Release of water from a few reservoirs is also timed to enhance ] boating, which also could be considered a recreational usage. Other examples are anglers, water skiers, nature enthusiasts and swimmers.


844 million people still lacked even a basic drinking water service in 2017.<ref name=":7">{{Cite book|last1=WHO|first1=UNICEF|url=https://www.susana.org/en/knowledge-hub/resources-and-publications/library/details/2805|title=Progress on drinking water, sanitation and hygiene : 2017 update and SDG baselines.|year=2017|isbn=978-9241512893|location=Geneva|oclc=1010983346}}</ref>{{rp|3}} Of those, 159 million people worldwide drink water directly from surface water sources, such as lakes and streams.<ref name=":7" />{{rp|3}} One in eight people in the world do not have access to safe water.<ref>{{Cite web|date=2018-11-09|title=Global WASH Fast Facts {{!}} Global Water, Sanitation and Hygiene {{!}} Healthy Water {{!}} CDC|url=https://www.cdc.gov/healthywater/global/wash_statistics.html|access-date=2019-04-09|website=www.cdc.gov|language=en-us}}</ref><ref>{{cite web|last=Water Aid|title=Water|url=http://www.wateraid.org/uk/what_we_do/the_need/5899.asp?gclid=CMvwnO7B164CFUcRfAodFkdffg|url-status=dead|archive-url=https://archive.today/20130416024534/http://www.wateraid.org/uk/what_we_do/the_need/5899.asp?gclid=CMvwnO7B164CFUcRfAodFkdffg|archive-date=16 April 2013|access-date=17 March 2012}}</ref>
Recreational usage is usually non-consumptive. ]s are often targeted as using excessive amounts of water, especially in drier regions. It is, however, unclear whether recreational irrigation (which would include private gardens) has a noticeable effect on water resources. This is largely due to the unavailability of reliable data. Additionally, many golf courses utilize either primarily or exclusively treated effluent water, which has little impact on potable water availability.
== Challenges and threats ==
=== Water scarcity ===


{{excerpt|Water scarcity|paragraphs=1|file=no}}
Some governments, including the Californian Government, have labelled golf course usage as agricultural in order to deflect ]s' charges of wasting water. However, using the above figures as a basis, the actual statistical effect of this reassignment is close to zero. In Arizona, an organized lobby has been established in the form of the Golf Industry Association, a group focused on educating the public on how golf impacts the environment.


=== Water pollution ===
Recreational usage may reduce the availability of water for other users at specific times and places. For example, water retained in a reservoir to allow boating in the late summer is not available to farmers during the spring planting season. Water released for whitewater rafting may not be available for hydroelectric generation during the time of peak electrical demand.
{{-}}


]
===Environmental===


{{excerpt|water pollution|paragraphs=1|file=no}}
Explicit environmental water use is also a very small but growing percentage of total water use. Environmental water usage includes artificial wetlands, artificial lakes intended to create wildlife habitat, ]s , and water releases from reservoirs timed to help fish spawn.


=== Water conflict ===
Like recreational usage, environmental usage is non-consumptive but may reduce the availability of water for other users at specific times and places. For example, water release from a reservoir to help fish spawn may not be available to farms upstream.


{{excerpt|Water conflict|paragraphs=1}} <!-- this takes the first paragraph of the lead of the sub-article -->
==Water stress==
]


=== Climate change ===
{{Main|Water crisis|Water stress}}
{{Further|Effects of climate change on the water cycle}}
The concept of water stress is relatively simple: According to the ], it applies to situations where there is not enough water for all uses, whether agricultural, industrial or domestic.
{{excerpt|Water security#Climate change|paragraphs=1|file=no}}<!-- this takes the first two paragraphs of the lead of the sub-article -->
Defining thresholds for stress in terms of available water ] is more complex, however, entailing assumptions about water use and its efficiency. Nevertheless, it has been proposed that when annual per capita renewable freshwater availability is less than 1,700 cubic meters, countries begin to experience periodic or regular water stress. Below 1,000 cubic meters, water
scarcity begins to hamper economic development and human health and well-being.


=== Groundwater overdrafting ===
===Population growth===
The world's supply of ] is steadily decreasing. Groundwater depletion (or ]) is occurring for example in Asia, South America and North America. It is still unclear how much natural renewal ] this usage, and whether ]s are threatened.<ref>{{cite journal |last1=Gleeson |first1=Tom |last2=Wada |first2=Yoshihide |last3=Bierkens |first3=Marc F. P. |last4=van Beek |first4=Ludovicus P. H. |date=9 August 2012 |title=Water balance of global aquifers revealed by groundwater footprint |journal=] |volume=488 |issue=7410 |pages=197–200 |bibcode=2012Natur.488..197G |doi=10.1038/nature11295 |pmid=22874965 |s2cid=4393813}}</ref>
In 2000, the world population was 6.2 billion. The UN estimates that by 2050 there will be an additional 3.5 billion people with most of the growth in ] that already suffer water stress.<ref>{{cite web|url=http://www.un.org/apps/news/story.asp?NewsID=13451&Cr=population&Cr1 |title=World population to reach 9.1 billion in 2050, UN projects |publisher=Un.org |date=2005-02-24 |accessdate=2009-03-12}}</ref> Thus, water demand will increase unless there are corresponding increases in ] and ] of this vital resource.<ref>{{cite web|url=http://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fwww.pubmedcentral.nih.gov%2Farticlerender.fcgi%3Fartid%3D1693287&ei=q9vnRsOEJpmSwQHny8TfBQ&usg=AFQjCNHS5RKSHrKezWO_PBtqp06oMAZs8Q&sig2=becO6aqfyo1izUxdiBcILg |title=Groundwater – the processes and global significance of aquifer degradation |doi=10.1098/rstb.2003.1380 |publisher=Google.com |date=2003-12-29 |accessdate=2009-03-12}}</ref>
{{excerpt|overdrafting|paragraphs=1}}


== Water resource management ==
===Expansion of business activity===
{{Further|Research Institute for Groundwater|Water resources law|}}
Business activity ranging from industrialization to services such as tourism and entertainment continues to expand rapidly. This expansion requires increased water services including both ] and sanitation, which can lead to more pressure on water resources and natural ]s.


]). Water resources 1961-90, water use around 2000. Computed by the global freshwater model ].]]
===Rapid urbanization===
The trend towards ] is accelerating. Small private ] and ]s that work well in low-density communities are not feasible within high-density ]s. Urbanization requires significant investment in water ] in order to deliver water to individuals and to process the concentrations of wastewater – both from individuals and from business. These polluted and contaminated waters must be treated or they pose unacceptable public health risks.


Water resource management is the activity of planning, developing, distributing and managing the optimum use of water resources. It is an aspect of ]. The field of water resources management will have to continue to adapt to the current and future issues facing the allocation of water. With the growing uncertainties of global ] and the long-term impacts of past management actions, this decision-making will be even more difficult. It is likely that ongoing climate change will lead to situations that have not been encountered. As a result, alternative management strategies, including participatory approaches and ] are increasingly being used to strengthen water decision-making.
In 60% of European cities with more than 100,000 people, groundwater is being used at a faster rate than it can be replenished.<ref>{{cite web|url=http://reports.eea.europa.eu/92-826-5409-5/en |title=Europe’s Environment: The Dobris Assessment |publisher=Reports.eea.europa.eu |date=1995-05-20 |accessdate=2009-03-12}}</ref> Even if some water remains available, it ] to capture it.


Ideally, water resource management planning has regard to all the competing ] and seeks to allocate water on an equitable basis to satisfy all uses and demands. As with other ], this is rarely possible in practice so decision-makers must prioritise issues of sustainability, equity and factor optimisation (in that order!) to achieve acceptable outcomes. One of the biggest concerns for water-based resources in the future is the ] of the current and future water resource allocation.
===Climate change===
] could have significant impacts on water resources around the world because of the close connections between the climate and ]. Rising temperatures will increase ] and lead to increases in precipitation, though there will be regional variations in ]. Overall, the global supply of freshwater will increase. Both ] and ] may become more frequent in different regions at different times, and dramatic changes in ] and ] are expected in mountainous areas. Higher temperatures will also affect water quality in ways that are not well understood. Possible impacts include increased ]. Climate change could also mean an increase in demand for farm irrigation, garden sprinklers, and perhaps even swimming pools


] has a target related to water resources management: "Target 6.5: By 2030, implement integrated water resources management at all levels, including through transboundary cooperation as appropriate."<ref name=":3">Ritchie, Roser, Mispy, Ortiz-Ospina (2018) ''SDG-Tracker.org, website''</ref><ref name=":17">United Nations (2017) Resolution adopted by the General Assembly on 6 July 2017, ] ()</ref>
===Depletion of aquifers===
Due to the ], competition for water is growing such that many of the worlds major aquifers are becoming depleted. This is due both for direct human consumption as well as agricultural irrigation by groundwater. Millions of ] of all sizes are currently extracting groundwater throughout the world. Irrigation in dry areas such as northern China and India is supplied by groundwater, and is being extracted at an unsustainable rate.
Cities that have experienced aquifer drops between 10 to 50 meters include ], ], ], ], ] and ].<ref>{{cite web|url=http://www-wds.worldbank.org/external/default/main?pagePK=64193027&piPK=64187937&theSitePK=523679&menuPK=64187510&searchMenuPK=64187283&siteName=WDS&entityID=000009265_3980429110739 |title=Groundwater in Urban Development |publisher=Wds.worldbank.org |date= |accessdate=2009-03-12}}</ref>


===Pollution and water protection=== === Sustainable water management ===
At present, only about 0.08 percent of all the world's fresh water is accessible. And there is ever-increasing demand for ], ], ] and ]. Due to the small percentage of water available, optimizing the fresh water we have left from ] has been a growing challenge around the world.
{{Main|Water pollution}}
]


Much effort in water resource management is directed at optimizing the ] and in minimizing the ] of water use on the natural environment. The observation of water as an integral part of the ] is based on ], based on the 1992 ] (see below).
] is one of the main concerns of the world today. The governments of numerous countries have strived to find solutions to reduce this problem. Many pollutants threaten water supplies, but the most widespread, especially in developing countries, is the discharge of raw ] into natural waters; this method of sewage disposal is the most common method in underdeveloped countries, but also is prevalent in quasi-developed countries such as China, India and Iran.
Sewage, sludge, garbage, and even toxic pollutants are all dumped into the water. Even if sewage is treated, problems still arise. Treated sewage forms sludge, which may be placed in landfills, spread out on land, incinerated or dumped at sea.<ref>Ocean dumping of sewage sludge is prohibited in the United States by the ] (MPRSA).</ref> In addition to sewage, ] such as ] runoff is a significant source of pollution in some parts of the world, along with urban ] runoff and ]s dumped by industries and governments.


Sustainable water management requires a holistic approach based on the principles of ], originally articulated in 1992 at the Dublin (January) and Rio (July) conferences. The four Dublin Principles, promulgated in the ] are:
===Water and conflict===
The only known example of an actual inter-state conflict over water took place between 2500 and 2350 BC between the ]n states of ] and ].<ref>Rasler, Karen A. and W. R. Thompson. "Contested Territory, Strategic Rivalries, and Conflict Escalation." International Studies Quarterly. 50. 1. (2006): 145-168.</ref> Yet, despite the lack of evidence of international ]s being fought over water alone, water has been the source of various conflicts throughout history. When water ] causes political tensions to arise, this is referred to as water stress. Water stress has led most often to conflicts at local and regional levels.<ref>Wolf, Aaron T. “Water and Human Security.” Journal of Contemporary Water Research and Education. 118. (2001): 29</ref> Using a purely quantitative methodology, Thomas Homer-Dixon successfully correlated water scarcity and scarcity of available arable lands to an increased chance of violent conflict.<ref name="Homer-Dixon">Homer-Dixon, Thomas. "Environment, Scarcity, and Violence." Princeton University Press. (1999).</ref>


# Fresh water is a finite and vulnerable resource, essential to sustain life, development and the environment;
Water stress can also exacerbate conflicts and ] tensions which are not directly caused by water. Gradual reductions over time in the quality and/or quantity of fresh water can add to the instability of a region by depleting the health of a population, obstructing ], and exacerbating larger conflicts.<ref name="Postel">Postel, S. L. and A. T. Wolf. “Dehydrating Conflict.” Foreign Policy. 126. (2001): 60-67.</ref>
# Water development and management should be based on a participatory approach, involving users, planners and policy-makers at all levels;
# Women play a central part in the provision, management and safeguarding of water;
# Water has an economic value in all its competing uses and should be recognized as an economic good.


Implementation of these principles has guided reform of national water management law around the world since 1992.
Conflicts and tensions over water are most likely to arise within national borders, in the downstream areas of distressed ] basins. Areas such as the lower regions of ]'s ] or the ] in ], for example, have already been experiencing water stress for several years. Additionally, certain arid countries which rely heavily on water for irrigation, such as China, ], ], and ], are particularly at risk of water-related conflicts.<ref name="Postel"/> Political tensions, civil protest, and violence may also occur in reaction to ]. The ] are a case in point.


Further challenges to sustainable and equitable water resources management include the fact that many water bodies are shared across boundaries which may be international (see ]) or intra-national (see ]).
==World water supply and distribution==
Food and water are two basic human needs. However, global coverage figures from 2002 indicate that, of every 10 people:
* roughly 5 have a connection to a piped water supply at home (in their dwelling, plot or yard);
* 3 make use of some other sort of improved water supply, such as a protected well or public standpipe;
* 2 are unserved;
* In addition, 4 out of every 10 people live without improved sanitation.<ref name="WBCSD Water Facts & Trends"/>


===Integrated water resources management===
At ] governments approved a Plan of Action to:
{{See also|Integrated Flood Management}}
* Halve by 2015 the proportion of people unable to reach or afford safe drinking water. The defines "Reasonable access" to water as at least 20 liters per person per day from a source within one kilometer of the user’s home.
Integrated water resources management (IWRM) has been defined by the ] as "a process which promotes the coordinated ] and management of water, land and related resources, in order to maximize the resultant ] and ] in an equitable manner without compromising the ] of vital ]s".<ref>{{Cite web|title=International Decade for Action 'Water for Life' 2005-2015. Focus Areas: Integrated Water Resources Management (IWRM)|url=https://www.un.org/waterforlifedecade/iwrm.shtml#:~:text=It%20states:%20%27IWRM%20is%20a,the%20sustainability%20of%20vital%20ecosystems.|access-date=2020-11-18|website=www.un.org|language=EN}}</ref>
* Halve the proportion of people without access to basic sanitation. The GWSSR defines "Basic sanitation" as private or shared but not public disposal systems that separate waste from human contact.


Some scholars say that IWRM is complementary to ] because water security is a goal or destination, whilst IWRM is the process necessary to achieve that goal.<ref name=":1">{{cite book |last1=Sadoff |first1=Claudia |title=Oxford Research Encyclopedia of Environmental Science |last2=Grey |first2=David |last3=Borgomeo |first3=Edoardo |year=2020 |isbn=978-0-19-938941-4 |chapter=Water Security |doi=10.1093/acrefore/9780199389414.013.609}}</ref>
<!-- Image with unknown copyright status removed: ] -->
As the picture shows, in 2025, water shortages will be more prevalent among poorer countries where resources are limited and population growth is rapid, such as the ], ], and parts of ]. By 2025, large urban and peri-urban areas will require new infrastructure to provide safe water and adequate sanitation. This suggests growing conflicts with agricultural water users, who currently consume the majority of the water used by humans.


IWRM is a paradigm that emerged at international conferences in the late 1900s and early 2000s, although participatory water management institutions have existed for centuries.<ref name=":0">{{Cite journal |last1=Rahaman |first1=Muhammad Mizanur |last2=Varis |first2=Olli |date=April 2005 |title=Integrated water resources management: evolution, prospects and future challenges |journal=Sustainability: Science, Practice and Policy |language=en |volume=1 |issue=1 |pages=15–21 |doi=10.1080/15487733.2005.11907961 |s2cid=10057051 |issn=1548-7733|doi-access=free |bibcode=2005SSPP....1...15R }}</ref> Discussions on a holistic way of managing water resources began already in the 1950s leading up to the 1977 United Nations Water Conference.<ref>Asit K.B. (2004). Integrated Water Resources Management: A Reassessment, Water International, 29(2), 251</ref> The development of IWRM was particularly recommended in the final statement of the ministers at the International Conference on Water and the Environment in 1992, known as the ]. This concept aims to promote changes in practices which are considered fundamental to improved ]. IWRM was a topic of ], which was attended by a more varied group of stakeholders than the preceding conferences and contributed to the creation of the GWP.<ref name=":0" />
Generally speaking the more developed countries of ], ] and ] will not see a serious threat to water supply by the year 2025, not only because of their relative wealth, but more importantly their populations will be better aligned with available water resources. North Africa, the Middle East, ] and northern China will face very severe water shortages due to physical scarcity and a condition of overpopulation relative to their ] with respect to water supply. Most of ], ] Africa, Southern China and India will face water supply shortages by 2025; for these latter regions the causes of scarcity will be economic constraints to developing safe drinking water, as well as excessive ].


In the ] definition, IWRM rests upon three principles that together act as the overall framework:<ref>{{Cite web|title=Integrated Water Resources Management: Basic Concepts {{!}} IWA Publishing|url=https://www.iwapublishing.com/news/integrated-water-resources-management-basic-concepts|access-date=2020-11-18|website=www.iwapublishing.com}}</ref>
1.6 billion people have gained access to a safe water source since 1990.
# Social equity: ensuring equal access for all users (particularly marginalized and poorer user groups) to an adequate quantity and quality of water necessary to sustain human ].
<ref name="mdgs.un.org">http://mdgs.un.org/unsd/mdg/Resources/Static/Products/Progress2008/MDG_Report_2008_En.pdf#page=44</ref> The proportion of people in developing countries with access to safe water is calculated to have improved from 30 percent in 1970<ref>Björn Lomborg (2001), ''The Skeptical Environmentalist'' (Cambridge University Press), ISBN 0-521-01068-3, </ref> to 71 percent in 1990, 79 percent in 2000 and 84 percent in 2004. This trend is projected to continue.<ref name="mdgs.un.org"/>
# Economic efficiency: bringing the greatest benefit to the greatest number of users possible with the available financial and water resources.
# Ecological sustainability: requiring that ]s are acknowledged as users and that adequate allocation is made to sustain their natural functioning.
In 2002, the development of IWRM was discussed at ] held in Johannesburg, which aimed to encourage the implementation of IWRM at a global level.<ref>{{Citation|last1=Ibisch|first1=Ralf B.|title=Integrated Water Resources Management: Concept, Research and Implementation|date=2016|url=http://link.springer.com/10.1007/978-3-319-25071-7_1|pages=3–32|editor-last=Borchardt|editor-first=Dietrich|place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-319-25071-7_1|isbn=978-3-319-25069-4|access-date=2020-11-14|last2=Bogardi|first2=Janos J.|last3=Borchardt|first3=Dietrich|editor2-last=Bogardi|editor2-first=Janos J.|editor3-last=Ibisch|editor3-first=Ralf B.}}</ref> ] recommended IWRM and discussed information sharing, stakeholder participation, and gender and class dynamics.<ref name=":0" />


Operationally, IWRM approaches involve applying knowledge from various disciplines as well as the insights from diverse stakeholders to devise and implement efficient, equitable and sustainable solutions to water and development problems. As such, IWRM is a comprehensive, ] planning and implementation tool for managing and developing water resources in a way that balances social and economic needs, and that ensures the ] for future generations. In addition, in light of contributing the achievement of ],<ref>{{Cite book|url=http://link.springer.com/10.1007/978-3-319-75163-4|title=Managing Water, Soil and Waste Resources to Achieve Sustainable Development Goals|date=2018|publisher=Springer International Publishing|isbn=978-3-319-75162-7|editor-last=Hülsmann|editor-first=Stephan|location=Cham|language=en|doi=10.1007/978-3-319-75163-4|s2cid=135441230|editor-last2=Ardakanian|editor-first2=Reza}}</ref> IWRM has been evolving into more sustainable approach as it considers the Nexus approach, which is a cross-sectoral water resource management. The Nexus approach is based on the recognition that "water, energy and food are closely linked through global and local water, carbon and energy cycles or chains."
==Economic considerations==
Water supply and sanitation require a huge amount of capital ] in infrastructure such as pipe networks, pumping stations and water treatment works. It is estimated that ] (OECD) nations need to invest at least USD 200 billion per year to replace aging water infrastructure to guarantee supply, reduce leakage rates and protect water quality.<ref>{{cite web|url=http://www.water-academy.org/article.php3?id_article=27 |title=The cost of meeting the Johannesburg targets for drinking water |publisher=Water-academy.org |date=2004-06-22 |accessdate=2009-03-12}}</ref>


An IWRM approach aims at avoiding a fragmented approach of water resources management by considering the following aspects: Enabling environment, roles of Institutions, management Instruments. Some of the cross-cutting conditions that are also important to consider when implementing IWRM are: Political will and commitment, capacity development, adequate investment, ] and sustainable cost recovery, monitoring and evaluation. There is not one correct administrative model. The art of IWRM lies in selecting, adjusting and applying the right mix of these tools for a given situation. IWRM practices depend on context; at the operational level, the challenge is to translate the agreed principles into concrete action.
International attention has focused upon the needs of the developing countries. To meet the ] targets of halving the proportion of the population lacking access to safe drinking water and basic sanitation by 2015, current annual investment on the order of USD 10 to USD 15 billion would need to be roughly doubled. This does not include investments required for the maintenance of existing infrastructure.<ref></ref>


=== Managing water in urban settings ===
Once infrastructure is in place, operating water supply and sanitation systems entails significant ongoing costs to cover personnel, energy, chemicals, maintenance and other expenses. The sources of money to meet these capital and operational costs are essentially either user fees, public funds or some combination of the two.
] and municipal ] systems]]
{{Excerpt|Integrated urban water management|paragraphs=1-2|file=no}}


==By country==
But this is where the economics of water management start to become extremely complex as they intersect with social and broader economic policy. Such policy questions are beyond the scope of this article, which has concentrated on basic information about water availability and water use. They are, nevertheless, highly relevant to understanding how critical water issues will affect business and industry in terms of both risks and opportunities.
] and governance is handled differently by different countries. For example, in the ], the ] (USGS) and its partners monitor water resources, conduct research and inform the public about groundwater quality.<ref>{{Cite web |title=Water Resources |url=https://www.usgs.gov/mission-areas/water-resources |access-date=2021-09-17 |website=www.usgs.gov |language=en}}</ref> Water resources in specific countries are described below:

{{World topic|Water resources in|title=Water resources by country|noredlinks=yes|state=show}}
===Business response===
The ] in its engaged in a ] process to:
* Clarify and enhance understanding by business of the key issues and drivers of change related to water.
* Promote mutual understanding between the business community and non-business stakeholders on water management issues.
* Support effective business action as part of the solution to sustainable water management.

It concludes that:

* Business cannot survive in a society that thirsts.
* One does not have to be in the water business to have a ].
* Business is part of the solution, and its potential is driven by its engagement.
* Growing water issues and complexity will drive up costs.


==See also== ==See also==
{{Portal|Water}} {{Portal|Water}}
* ]
* ]
* ]
* ]
* {{annotated link|Socio-hydrology}}
* ]
* ] * {{annotated link|Virtual water}}
* {{annotated link|Water resources law}}
* ]
* {{annotated link|Water rights}}
* ]
* {{annotated link|Water storage}}
* ]
* ]
* ]
* ]
* ]
* ]
* ] (European action plan)

==Further reading==
* ] ''When the Rivers Run Dry: Water—The Defining Crisis of the Twenty-First Century'' Beacon Press, 2006, ISBN 0-8070-8572-3 ISBN 978-0-8070-8572-1

==Notes==

{{Reflist|2}}


==References== ==References==
{{Refbegin|2}} {{reflist|30em}}
{{More footnotes|date=October 2009}}
{{External links|date=October 2009}}
*
*
*
*
*
*
*
* by the ''Environment Agency''
* from the ''University of California, Geology Department''
* from the ''University of California, Geology Department''
*
*
*
* from the ]
* {{PDFlink||3.71&nbsp;MB}} from the ] (CSIS) / ]
* , new directions in urban water usage.
*http://www.techstart.org/docs/ogpc_payment.pdf
*
*
* Food and Agriculture Organization of the United Nations
{{Refend}}


==External links== ==External links==
*
*
*
* One-stop resource for water information including drinking water, global water, and water resources (agricultural, industrial, medical).
*
*
*
*
*
*
*
*
* - Australian Government funded initiative supporting water management decision support tools
* Peace Palace Library
* — For information on OCONUS surface water and groundwater.
* — The UNESCO-IHE Institute for Water Education.
* Journalistic project on Water in South Asia at the Pulitzer Center on Crisis Reporting


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Latest revision as of 19:08, 29 October 2024

Sources of water that are potentially useful for humans This article is about all types of waters that are of potential use to humans. For a naturally occurring type of water resource that humans use a lot, see fresh water.

Distribution of freshwater resources by type

  Glaciers (69%)  Groundwater (30%)  Other Freshwater (e.g., Soil Moisture) (0.7%)  Directly Accessible Water (0.3%)

Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. These resources can be either freshwater from natural sources, or water produced artificially from other sources, such as from reclaimed water (wastewater) or desalinated water (seawater). 97% of the water on Earth is salt water and only three percent is fresh water; slightly over two-thirds of this is frozen in glaciers and polar ice caps. The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air. Natural sources of fresh water include surface water, under river flow, groundwater and frozen water. People use water resources for agricultural, industrial and household activities.

Water resources are under threat from multiple issues. There is water scarcity, water pollution, water conflict and climate change. Fresh water is in principle a renewable resource. However, the world's supply of groundwater is steadily decreasing. Groundwater depletion (or overdrafting) is occurring for example in Asia, South America and North America.

Natural sources of fresh water

Further information: Water distribution on Earth

Natural sources of fresh water include surface water, under river flow, groundwater and frozen water.

Surface water

Main article: Surface water
Lake Chungará and Parinacota volcano in northern Chile

Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, evapotranspiration and groundwater recharge. The only natural input to any surface water system is precipitation within its watershed. The total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial reservoirs, the permeability of the soil beneath these storage bodies, the runoff characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water loss.

Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing the stream flow.

Natural surface water can be augmented by importing surface water from another watershed through a canal or pipeline.

Brazil is estimated to have the largest supply of fresh water in the world, followed by Russia and Canada.

Water from glaciers

Glacier runoff is considered to be surface water. The Himalayas, which are often called "The Roof of the World", contain some of the most extensive and rough high altitude areas on Earth as well as the greatest area of glaciers and permafrost outside of the poles. Ten of Asia's largest rivers flow from there, and more than a billion people's livelihoods depend on them. To complicate matters, temperatures there are rising more rapidly than the global average. In Nepal, the temperature has risen by 0.6 degrees Celsius over the last decade, whereas globally, the Earth has warmed approximately 0.7 degrees Celsius over the last hundred years.

Groundwater

Relative groundwater travel times in the subsurface
This section is an excerpt from Groundwater.

Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.

Typically, groundwater is thought of as water flowing through shallow aquifers, but, in the technical sense, it can also contain soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water. Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earth's subsurface contains some water, which may be mixed with other fluids in some instances.

Under river flow

Throughout the course of a river, the total volume of water transported downstream will often be a combination of the visible free water flow together with a substantial contribution flowing through rocks and sediments that underlie the river and its floodplain called the hyporheic zone. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. The hyporheic zone often forms a dynamic interface between surface water and groundwater from aquifers, exchanging flow between rivers and aquifers that may be fully charged or depleted. This is especially significant in karst areas where pot-holes and underground rivers are common.

Artificial sources of usable water

There are several artificial sources of fresh water. One is treated wastewater (reclaimed water). Another is atmospheric water generators. Desalinated seawater is another important source. It is important to consider the economic and environmental side effects of these technologies.

Wastewater reuse

This section is an excerpt from Reclaimed water.

Water reclamation is the process of converting municipal wastewater or sewage and industrial wastewater into water that can be reused for a variety of purposes . It is also called wastewater reuse, water reuse or water recycling. There are many types of reuse. It is possible to reuse water in this way in cities or for irrigation in agriculture. Other types of reuse are environmental reuse, industrial reuse, and reuse for drinking water, whether planned or not. Reuse may include irrigation of gardens and agricultural fields or replenishing surface water and groundwater. This latter is also known as groundwater recharge. Reused water also serve various needs in residences such as toilet flushing, businesses, and industry. It is possible to treat wastewater to reach drinking water standards. Injecting reclaimed water into the water supply distribution system is known as direct potable reuse. Drinking reclaimed water is not typical. Reusing treated municipal wastewater for irrigation is a long-established practice. This is especially so in arid countries. Reusing wastewater as part of sustainable water management allows water to remain an alternative water source for human activities. This can reduce scarcity. It also eases pressures on groundwater and other natural water bodies.

There are several technologies used to treat wastewater for reuse. A combination of these technologies can meet strict treatment standards and make sure that the processed water is hygienically safe, meaning free from pathogens. The following are some of the typical technologies: Ozonation, ultrafiltration, aerobic treatment (membrane bioreactor), forward osmosis, reverse osmosis, and advanced oxidation, or activated carbon. Some water-demanding activities do not require high grade water. In this case, wastewater can be reused with little or no treatment.

Desalinated water

This section is an excerpt from Desalination.

Desalination is a process that removes mineral components from saline water. More generally, desalination is the removal of salts and minerals from a substance. One example is soil desalination. This is important for agriculture. It is possible to desalinate saltwater, especially sea water, to produce water for human consumption or irrigation. The by-product of the desalination process is brine. Many seagoing ships and submarines use desalination. Modern interest in desalination mostly focuses on cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few water resources independent of rainfall.

Due to its energy consumption, desalinating sea water is generally more costly than fresh water from surface water or groundwater, water recycling and water conservation; however, these alternatives are not always available and depletion of reserves is a critical problem worldwide. Desalination processes are using either thermal methods (in the case of distillation) or membrane-based methods (e.g. in the case of reverse osmosis).

Research into other options

Schematic illustration of a proposed approach for capturing moisture above the ocean surface and transporting it to proximal land for improving water security

Researchers proposed air capture over oceans which would "significantly increasing freshwater through the capture of humid air over oceans" to address present and, especially, future water scarcity/insecurity.

A 2021 study proposed hypothetical portable solar-powered atmospheric water harvesting devices. However, such off-the-grid generation may sometimes "undermine efforts to develop permanent piped infrastructure" among other problems.

Water uses

Total renewable freshwater resources of the world, in mm/year (1 mm is equivalent to 1 L of water per m) (long-term average for the years 1961–1990). Resolution is 0.5° longitude x 0.5° latitude (equivalent to 55 km x 55 km at the equator). Computed by the global freshwater model WaterGAP.
Map of water stress and spatial variability of water yield along the delineated near-offshore region of 200 km across the world

The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many farms require large quantities of water in the spring, and no water at all in the winter. Other users have a continuous need for water, such as a power plant that requires water for cooling. Over the long term the average rate of precipitation within a watershed is the upper bound for average consumption of natural surface water from that watershed.

Agriculture and other irrigation

Further information: Sustainable Water and Innovative Irrigation Management This section is an excerpt from Irrigation.
Irrigation of agricultural fields in Andalusia, Spain. Irrigation canal on the left.

Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been developed by many cultures around the world. Irrigation helps to grow crops, maintain landscapes, and revegetate disturbed soils in dry areas and during times of below-average rainfall. In addition to these uses, irrigation is also employed to protect crops from frost, suppress weed growth in grain fields, and prevent soil consolidation. It is also used to cool livestock, reduce dust, dispose of sewage, and support mining operations. Drainage, which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation.

There are several methods of irrigation that differ in how water is supplied to plants. Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure water devices. Micro-irrigation is a system that distributes water under low pressure through a piped network and applies it as a small discharge to each plant. Micro-irrigation uses less pressure and water flow than sprinkler irrigation. Drip irrigation delivers water directly to the root zone of plants. Subirrigation has been used in field crops in areas with high water tables for many years. It involves artificially raising the water table to moisten the soil below the root zone of plants.

Irrigation water can come from groundwater (extracted from springs or by using wells), from surface water (withdrawn from rivers, lakes or reservoirs) or from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection. Irrigation can be supplementary to rainfall, which is common in many parts of the world as rainfed agriculture, or it can be full irrigation, where crops rarely rely on any contribution from rainfall. Full irrigation is less common and only occurs in arid landscapes with very low rainfall or when crops are grown in semi-arid areas outside of rainy seasons.

Industries

See also: Industrial water treatment and Industrial wastewater treatment

It is estimated that 22% of worldwide water is used in industry. Major industrial users include hydroelectric dams, thermoelectric power plants, which use water for cooling, ore and oil refineries, which use water in chemical processes, and manufacturing plants, which use water as a solvent. Water withdrawal can be very high for certain industries, but consumption is generally much lower than that of agriculture.

Water is used in renewable power generation. Hydroelectric power derives energy from the force of water flowing downhill, driving a turbine connected to a generator. This hydroelectricity is a low-cost, non-polluting, renewable energy source. Significantly, hydroelectric power can also be used for load following unlike most renewable energy sources which are intermittent. Ultimately, the energy in a hydroelectric power plant is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes and flows downhill. Pumped-storage hydroelectric plants also exist, which use grid electricity to pump water uphill when demand is low, and use the stored water to produce electricity when demand is high.

Thermoelectric power plants using cooling towers have high consumption, nearly equal to their withdrawal, as most of the withdrawn water is evaporated as part of the cooling process. The withdrawal, however, is lower than in once-through cooling systems.

Water is also used in many large scale industrial processes, such as thermoelectric power production, oil refining, fertilizer production and other chemical plant use, and natural gas extraction from shale rock. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes and increased water temperature (thermal pollution).

Drinking water and domestic use (households)

Main articles: Water supply, Drinking water, and Water footprint
Drinking water

It is estimated that 8% of worldwide water use is for domestic purposes. These include drinking water, bathing, cooking, toilet flushing, cleaning, laundry and gardening. Basic domestic water requirements have been estimated by Peter Gleick at around 50 liters per person per day, excluding water for gardens.

Drinking water is water that is of sufficiently high quality so that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries, the water supplied to domestic, commerce and industry is all of drinking water standard even though only a very small proportion is actually consumed or used in food preparation.

844 million people still lacked even a basic drinking water service in 2017. Of those, 159 million people worldwide drink water directly from surface water sources, such as lakes and streams. One in eight people in the world do not have access to safe water.

Challenges and threats

Water scarcity

This section is an excerpt from Water scarcity. Water scarcity (closely related to water stress or water crisis) is the lack of fresh water resources to meet the standard water demand. There are two types of water scarcity. One is physical. The other is economic water scarcity. Physical water scarcity is where there is not enough water to meet all demands. This includes water needed for ecosystems to function. Regions with a desert climate often face physical water scarcity. Central Asia, West Asia, and North Africa are examples of arid areas. Economic water scarcity results from a lack of investment in infrastructure or technology to draw water from rivers, aquifers, or other water sources. It also results from weak human capacity to meet water demand. Many people in Sub-Saharan Africa are living with economic water scarcity.

Water pollution

Polluted water
This section is an excerpt from Water pollution.

Water pollution (or aquatic pollution) is the contamination of water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources. These are sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Water pollution may affect either surface water or groundwater. This form of pollution can lead to many problems. One is the degradation of aquatic ecosystems. Another is spreading water-borne diseases when people use polluted water for drinking or irrigation. Water pollution also reduces the ecosystem services such as drinking water provided by the water resource.

Water conflict

This section is an excerpt from Water conflict.
Ethiopia's move to fill the dam's reservoir could reduce Nile flows by as much as 25% and devastate Egyptian farmlands.
Water conflict typically refers to violence or disputes associated with access to, or control of, water resources, or the use of water or water systems as weapons or casualties of conflicts. The term water war is colloquially used in media for some disputes over water, and often is more limited to describing a conflict between countries, states, or groups over the rights to access water resources. The United Nations recognizes that water disputes result from opposing interests of water users, public or private. A wide range of water conflicts appear throughout history, though they are rarely traditional wars waged over water alone. Instead, water has long been a source of tension and one of the causes for conflicts. Water conflicts arise for several reasons, including territorial disputes, a fight for resources, and strategic advantage.

Climate change

Further information: Effects of climate change on the water cycle This section is an excerpt from Water security § Climate change. Impacts of climate change that are tied to water, affect people's water security on a daily basis. They include more frequent and intense heavy precipitation which affects the frequency, size and timing of floods. Also droughts can alter the total amount of freshwater and cause a decline in groundwater storage, and reduction in groundwater recharge. Reduction in water quality due to extreme events can also occur. Faster melting of glaciers can also occur.

Groundwater overdrafting

The world's supply of groundwater is steadily decreasing. Groundwater depletion (or overdrafting) is occurring for example in Asia, South America and North America. It is still unclear how much natural renewal balances this usage, and whether ecosystems are threatened.

This section is an excerpt from Overdrafting.
Within a long period of groundwater depletion in California's Central Valley, short periods of recovery were mostly driven by extreme weather events that typically caused flooding and had negative social, environmental and economic consequences.
Overdrafting is the process of extracting groundwater beyond the equilibrium yield of an aquifer. Groundwater is one of the largest sources of fresh water and is found underground. The primary cause of groundwater depletion is the excessive pumping of groundwater up from underground aquifers. Insufficient recharge can lead to depletion, reducing the usefulness of the aquifer for humans. Depletion can also have impacts on the environment around the aquifer, such as soil compression and land subsidence, local climatic change, soil chemistry changes, and other deterioration of the local environment.

Water resource management

Further information: Research Institute for Groundwater and Water resources law
Global values of water resources and human water use (excluding Antarctica). Water resources 1961-90, water use around 2000. Computed by the global freshwater model WaterGAP.

Water resource management is the activity of planning, developing, distributing and managing the optimum use of water resources. It is an aspect of water cycle management. The field of water resources management will have to continue to adapt to the current and future issues facing the allocation of water. With the growing uncertainties of global climate change and the long-term impacts of past management actions, this decision-making will be even more difficult. It is likely that ongoing climate change will lead to situations that have not been encountered. As a result, alternative management strategies, including participatory approaches and adaptive capacity are increasingly being used to strengthen water decision-making.

Ideally, water resource management planning has regard to all the competing demands for water and seeks to allocate water on an equitable basis to satisfy all uses and demands. As with other resource management, this is rarely possible in practice so decision-makers must prioritise issues of sustainability, equity and factor optimisation (in that order!) to achieve acceptable outcomes. One of the biggest concerns for water-based resources in the future is the sustainability of the current and future water resource allocation.

Sustainable Development Goal 6 has a target related to water resources management: "Target 6.5: By 2030, implement integrated water resources management at all levels, including through transboundary cooperation as appropriate."

Sustainable water management

At present, only about 0.08 percent of all the world's fresh water is accessible. And there is ever-increasing demand for drinking, manufacturing, leisure and agriculture. Due to the small percentage of water available, optimizing the fresh water we have left from natural resources has been a growing challenge around the world.

Much effort in water resource management is directed at optimizing the use of water and in minimizing the environmental impact of water use on the natural environment. The observation of water as an integral part of the ecosystem is based on integrated water resources management, based on the 1992 Dublin Principles (see below).

Sustainable water management requires a holistic approach based on the principles of Integrated Water Resource Management, originally articulated in 1992 at the Dublin (January) and Rio (July) conferences. The four Dublin Principles, promulgated in the Dublin Statement are:

  1. Fresh water is a finite and vulnerable resource, essential to sustain life, development and the environment;
  2. Water development and management should be based on a participatory approach, involving users, planners and policy-makers at all levels;
  3. Women play a central part in the provision, management and safeguarding of water;
  4. Water has an economic value in all its competing uses and should be recognized as an economic good.

Implementation of these principles has guided reform of national water management law around the world since 1992.

Further challenges to sustainable and equitable water resources management include the fact that many water bodies are shared across boundaries which may be international (see water conflict) or intra-national (see Murray-Darling basin).

Integrated water resources management

See also: Integrated Flood Management

Integrated water resources management (IWRM) has been defined by the Global Water Partnership (GWP) as "a process which promotes the coordinated development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems".

Some scholars say that IWRM is complementary to water security because water security is a goal or destination, whilst IWRM is the process necessary to achieve that goal.

IWRM is a paradigm that emerged at international conferences in the late 1900s and early 2000s, although participatory water management institutions have existed for centuries. Discussions on a holistic way of managing water resources began already in the 1950s leading up to the 1977 United Nations Water Conference. The development of IWRM was particularly recommended in the final statement of the ministers at the International Conference on Water and the Environment in 1992, known as the Dublin Statement. This concept aims to promote changes in practices which are considered fundamental to improved water resource management. IWRM was a topic of the second World Water Forum, which was attended by a more varied group of stakeholders than the preceding conferences and contributed to the creation of the GWP.

In the International Water Association definition, IWRM rests upon three principles that together act as the overall framework:

  1. Social equity: ensuring equal access for all users (particularly marginalized and poorer user groups) to an adequate quantity and quality of water necessary to sustain human well-being.
  2. Economic efficiency: bringing the greatest benefit to the greatest number of users possible with the available financial and water resources.
  3. Ecological sustainability: requiring that aquatic ecosystems are acknowledged as users and that adequate allocation is made to sustain their natural functioning.

In 2002, the development of IWRM was discussed at the World Summit on Sustainable Development held in Johannesburg, which aimed to encourage the implementation of IWRM at a global level. The third World Water Forum recommended IWRM and discussed information sharing, stakeholder participation, and gender and class dynamics.

Operationally, IWRM approaches involve applying knowledge from various disciplines as well as the insights from diverse stakeholders to devise and implement efficient, equitable and sustainable solutions to water and development problems. As such, IWRM is a comprehensive, participatory planning and implementation tool for managing and developing water resources in a way that balances social and economic needs, and that ensures the protection of ecosystems for future generations. In addition, in light of contributing the achievement of Sustainable Development goals (SDGs), IWRM has been evolving into more sustainable approach as it considers the Nexus approach, which is a cross-sectoral water resource management. The Nexus approach is based on the recognition that "water, energy and food are closely linked through global and local water, carbon and energy cycles or chains."

An IWRM approach aims at avoiding a fragmented approach of water resources management by considering the following aspects: Enabling environment, roles of Institutions, management Instruments. Some of the cross-cutting conditions that are also important to consider when implementing IWRM are: Political will and commitment, capacity development, adequate investment, financial stability and sustainable cost recovery, monitoring and evaluation. There is not one correct administrative model. The art of IWRM lies in selecting, adjusting and applying the right mix of these tools for a given situation. IWRM practices depend on context; at the operational level, the challenge is to translate the agreed principles into concrete action.

Managing water in urban settings

Typical urban water cycle depicting drinking water purification and municipal sewage treatment systems
This section is an excerpt from Integrated urban water management.

Integrated urban water management (IUWM) is the practice of managing freshwater, wastewater, and storm water as components of a basin-wide management plan. It builds on existing water supply and sanitation considerations within an urban settlement by incorporating urban water management within the scope of the entire river basin. IUWM is commonly seen as a strategy for achieving the goals of Water Sensitive Urban Design. IUWM seeks to change the impact of urban development on the natural water cycle, based on the premise that by managing the urban water cycle as a whole; a more efficient use of resources can be achieved providing not only economic benefits but also improved social and environmental outcomes. One approach is to establish an inner, urban, water cycle loop through the implementation of reuse strategies. Developing this urban water cycle loop requires an understanding both of the natural, pre-development, water balance and the post-development water balance. Accounting for flows in the pre- and post-development systems is an important step toward limiting urban impacts on the natural water cycle.

IUWM within an urban water system can also be conducted by performance assessment of any new intervention strategies by developing a holistic approach which encompasses various system elements and criteria including sustainability type ones in which integration of water system components including water supply, waste water and storm water subsystems would be advantageous. Simulation of metabolism type flows in urban water system can also be useful for analysing processes in urban water cycle of IUWM.

By country

Water resource management and governance is handled differently by different countries. For example, in the United States, the United States Geological Survey (USGS) and its partners monitor water resources, conduct research and inform the public about groundwater quality. Water resources in specific countries are described below:

Water resources by country
  • Argentina
  • Azerbaijan
  • Belize
  • Bolivia
  • Brazil
  • Chile
  • China
  • Colombia
  • Costa Rica
  • Djibouti
  • Dominican Republic
  • Egypt
  • El Salvador
  • Guatemala
  • Honduras
  • India
  • Jamaica
  • Jordan
  • Kyrgyzstan
  • Mexico
  • Nicaragua
  • Pakistan
  • Peru
  • Saudi Arabia
  • Syria
  • Uruguay
  • See also

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