Editing Resource depletion (section)

== Groundwater ==
[[File:Groundwater flow.svg|thumb|upright=1.75|Groundwater flow paths vary greatly in length, depth and travel time from points of recharge to points of discharge in the groundwater system.]]{{Main|Overdrafting}}
Water is an essential resource needed for survival. Water access has a profound influence on a society's prosperity and success.<ref>{{Cite journal|last1=Peterson|first1=Erik|last2=Posner|first2=Rachel|date=January 2010|title=The World's Water Challenge|journal=Current History|volume=109|issue=723|pages=31–34|doi=10.1525/curh.2010.109.723.31|doi-access=free}}</ref> [[Groundwater]] is water that is in saturated zones underground, the upper surface of the saturated zone is called the water table.<ref name=":6">{{Cite web|url=https://www.usgs.gov/faqs/what-groundwater?qt-news_science_products=0#qt-news_science_products|title=What is groundwater? |publisher=USGS |language=en|access-date=2019-04-02|archive-date=2019-04-03|archive-url=https://web.archive.org/web/20190403231526/https://www.usgs.gov/faqs/what-groundwater?qt-news_science_products=0#qt-news_science_products|url-status=live}}</ref> Groundwater is held in the pores and fractures of underground materials like sand, gravel and other rock, these rock materials are called aquifers.<ref name=":6" /> Groundwater can either flow naturally out of rock materials or can be pumped out. Groundwater supplies wells and aquifers for private, agricultural, and public use and is used by more than a third of the world's population every day for their drinking water. Globally there is 22.6 million cubic kilometers of groundwater available; of this, only 0.35 million of that is renewable.<ref name=":2">{{Cite web|url=http://www.cbc.ca/news/technology/groundwater-study-1.3318137|title=Most Groundwater is Effectively a Non-renewable Resource, Study Finds|last=Chung|first=Emily|publisher=CBC News|access-date=2017-07-08|archive-date=2017-06-15|archive-url=https://web.archive.org/web/20170615151405/http://www.cbc.ca/news/technology/groundwater-study-1.3318137|url-status=live}}</ref>

=== Groundwater as a non-renewable resource ===
Groundwater is considered to be a non-renewable resource because less than six percent of the water around the world is replenished and renewed on a human timescale of 50 years.<ref>{{Cite web|url=https://www.cbc.ca/news/technology/groundwater-study-1.3318137|title=Most groundwater is effectively a non-renewable resource, study finds|access-date=2020-03-19|archive-date=2019-09-29|archive-url=https://web.archive.org/web/20190929020604/https://www.cbc.ca/news/technology/groundwater-study-1.3318137|url-status=live}}</ref> People are already using non-renewable water that is thousands of years old, in areas like Egypt they are using water that may have been renewed a million years ago which is not renewable on human timescales.<ref name=":2" /> Of the groundwater used for agriculture, 16–33% is non-renewable.<ref name=":7">{{Cite journal|last1=Wada|first1=Yoshihide|last2=Beek|first2=Ludovicus P. H. van|last3=Kempen|first3=Cheryl M. van|last4=Reckman|first4=Josef W. T. M.|last5=Vasak|first5=Slavek|last6=Bierkens|first6=Marc F. P.|date=2010|title=Global depletion of groundwater resources|journal=Geophysical Research Letters|language=en|volume=37|issue=20|pages=n/a|doi=10.1029/2010GL044571|bibcode=2010GeoRL..3720402W|issn=1944-8007|url=https://dspace.library.uu.nl/bitstream/1874/209122/1/2010GL044571.pdf|hdl=1874/209122|s2cid=42843631|access-date=2019-09-02|archive-date=2024-04-22|archive-url=https://web.archive.org/web/20240422061543/https://dspace.library.uu.nl/bitstream/1874/209122/1/2010GL044571.pdf|url-status=live}}</ref> It is estimated that since the 1960s groundwater extraction has more than doubled, which has increased groundwater depletion.<ref name=":7" /> Due to this increase in depletion, in some of the most depleted areas use of groundwater for irrigation has become impossible or cost prohibitive.<ref name=":8">{{Cite journal|last1=Konikow|first1=Leonard F.|last2=Kendy|first2=Eloise|date=2005-03-01|title=Groundwater depletion: A global problem|journal=Hydrogeology Journal|language=en|volume=13|issue=1|pages=317–320|doi=10.1007/s10040-004-0411-8|bibcode=2005HydJ...13..317K|s2cid=21715061|issn=1435-0157}}</ref>

=== Environmental impacts ===
Overusing groundwater, old or young, can lower subsurface water levels and dry up streams, which could have a huge effect on ecosystems on the surface.<ref name=":2" /> When the most easily recoverable fresh groundwater is removed this leaves a residual with inferior water quality. This is in part from induced leakage from the land surface, confining layers or adjacent aquifers that contain saline or contaminated water.<ref name=":8" /> Worldwide the magnitude of groundwater depletion from storage may be so large as to constitute a measurable contributor to sea-level rise.<ref name=":7" />

=== Mitigation ===
Currently, societies respond to water-resource depletion by shifting management objectives from location and developing new supplies to augmenting conserving and reallocation of existing supplies.<ref name=":8" /> There are two different perspectives to groundwater depletion, the first is that depletion is considered literally and simply as a reduction in the volume of water in the saturated zone, regardless of water quality considerations.<ref name=":8" /> A second perspective views depletion as a reduction in the usable volume of fresh groundwater in storage.<ref name=":8" />

Augmenting supplies can mean improving water quality or increasing water quantity. Depletion due to quality considerations can be overcome by treatment, whereas large volume metric depletion can only be alleviated by decreasing discharge or increasing recharge.<ref name=":8" /> Artificial recharge of storm flow and treated municipal wastewater, has successfully reversed groundwater declines.<ref name=":8" /> In the future improved infiltration and recharge technologies will be more widely used to maximize the capture of runoff and treated wastewater.