Editing Water (section)

===Water resources===
{{Main|Water resources}}
Water resources are [[natural resource]]s of water that are potentially useful for humans,<ref>{{Cite encyclopedia |title=water resource |encyclopedia=Encyclopædia Britannica |url=https://www.britannica.com/science/water-resource |access-date=17 May 2022 |language=en |archive-date=2 October 2022 |archive-url=https://web.archive.org/web/20221002130105/https://www.britannica.com/science/water-resource |url-status=live }}</ref> for example as a source of drinking [[water supply]] or [[irrigation]] water. Water occurs as both "stocks" and "flows". Water can be stored as lakes, water vapor, groundwater or aquifers, and ice and snow. Of the total volume of global freshwater, an estimated 69 percent is stored in glaciers and permanent snow cover; 30 percent is in groundwater; and the remaining 1 percent in lakes, rivers, the atmosphere, and biota.<ref>{{Cite book |title=Water in Crisis |last=Gleick |first=Peter H. |date=1993 |publisher=[[Oxford University Press]] |isbn=0-19-507627-3 |edition= |location=New York |publication-date=1993 |page=[https://archive.org/details/waterincrisisgui00glei/page/13 13] |url=https://archive.org/details/waterincrisisgui00glei/page/13 }}</ref> The length of time water remains in storage is highly variable: some aquifers consist of water stored over thousands of years but lake volumes may fluctuate on a seasonal basis, decreasing during dry periods and increasing during wet ones. A substantial fraction of the water supply for some regions consists of water extracted from water stored in stocks, and when withdrawals exceed recharge, stocks decrease. By some estimates, as much as 30 percent of total water used for irrigation comes from unsustainable withdrawals of groundwater, causing [[overdrafting|groundwater depletion]].<ref>{{cite journal |first1=Yoshihide|last1=Wada |first2=L. P. H.|last2=Van Beek|first3=Marc F. P. |last3=Bierkens|title=Nonsustainable groundwater sustaining irrigation: A global assessment|journal=Water Resources Research |date= 2012 |volume=48 |issue=6 |pages=W00L06 |doi=10.1029/2011WR010562|bibcode=2012WRR....48.0L06W |doi-access=free }}</ref>