Fresh water: Difference between revisions - Wikipedia
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In [[desert]] areas, or areas with impoverished or dusty soils, rain-bearing winds can pick up [[sand]] and [[dust]] and this can be deposited elsewhere in precipitation and causing the freshwater flow to be measurably contaminated both by insoluble solids but also by the soluble components of those soils. Significant quantities of [[iron]] may be transported in this way including the well-documented transfer of iron-rich rainfall falling in Brazil derived from sand-storms in the [[Sahara]] in [[north Africa]].<ref>{{Cite journal |last1=Rizzolo |first1=Joana A. |last2=Barbosa |first2=Cybelli G. G. |last3=Borillo |first3=Guilherme C. |last4=Godoi |first4=Ana F. L. |last5=Souza |first5=Rodrigo A. F. |last6=Andreoli |first6=Rita V. |last7=Manzi |first7=Antônio O. |last8=Sá |first8=Marta O. |last9=Alves |first9=Eliane G. |last10=Pöhlker |first10=Christopher |last11=Angelis |first11=Isabella H. |last12=Ditas |first12=Florian |last13=Saturno |first13=Jorge |last14=Moran-Zuloaga |first14=Daniel |last15=Rizzo |first15=Luciana V. |date=22 February 2017 |title=Soluble iron nutrients in Saharan dust over the central Amazon rainforest |url=https://www.researchgate.net/publication/314247273 |journal=Atmospheric Chemistry and Physics |volume=17 |issue=4 |pages=2673–2687 |doi=10.5194/acp-17-2673-2017 |bibcode=2017ACP....17.2673R |via=ResearchGate|hdl=10536/DRO/DU:30091978 |hdl-access=free |doi-access=free }}</ref>
In Africa, it was revealed that groundwater controls are complex and do not correspond directly to a single factor. Groundwater showed greater resilience to climate change than expected, and areas with an increasing threshold between 0.34 and 0.39 aridity index exhibited significant sensitivity to climate change. Land-use could affect infiltration and runoff processes. The years of most recharge coincided with the most precipitation anomalies, such as during [[El Niño]] and [[La Niña]] events. Three precipitation-recharge sensitivities were distinguished: in super arid areas with more than 0.67 aridity index, there was constant recharge with little variation with precipitation; in most sites (arid, semi-arid, humid), annual recharge increased as annual precipitation remained above a certain threshold; and in complex areas down to 0.1 aridity index (focused recharge), there was very inconsistent recharge (low precipitation but high recharge). Understanding these relationships can lead to the development of sustainable strategies for water collection. This understanding is particularly crucial in Africa, where water resources are often scarce and climate change poses significant challenges.<ref>{{Citation |title=Global climate change impacts on Sub-Sahara Africa: The case of Nigeria’sNigeria's shorelines |url=http://dx.doi.org/10.3726/978-3-653-04584-0/15 |work=The Impact of Climate Change on Sub-Sahara Africa |date=2015 |access-date=2023-12-19 |publisher=Peter Lang|doi=10.3726/978-3-653-04584-0/15 |isbn=978-3-653-04584-0 }}</ref>
== Water distribution ==
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[[File:Earth's_water_distribution.svg|thumb|upright=1.2|A graphical distribution of the locations of water on Earth.{{efn|Only 3% of the Earth's water is fresh water. Most of it is in icecaps and glaciers (69%) and groundwater (30%), while all lakes, rivers and swamps combined only account for a small fraction (0.3%) of the Earth's total freshwater reserves.{{citation needed|date=November 2022}}}}]]
{{main|Water distribution on Earth}}
Saline water in [[ocean]]s, [[sea]]s and saline [[groundwater]] make up about 97% of all the water on [[Earth]]. Only 2.5–2.75% is fresh water, including 1.75–2% frozen in [[glacier]]s, [[ice]] and snow, 0.5–0.75% as fresh groundwater. The water table is the level below which all spaces are filled with water, while the area above this level, where spaces in the rock and soil contain both air and water, is known as the unsaturated zone. The water in this unsaturated zone is referred to as soil moisture.
Below the water table, the entire region is known as the saturated zone, and the water in this zone is called groundwater.<ref name=":0">{{Citation |title=Natural Quality of Water and Groundwater Contamination |date=2000-04-14 |url=http://dx.doi.org/10.1201/9781482278934-9 |work=Groundwater Contamination, Volume I |pages=35–56 |access-date=2023-12-19 |publisher=CRC Press|doi=10.1201/9781482278934-9 |isbn=978-0-429-18165-8 }}</ref> despite being a hidden resource whose value is often overlooked,Groundwater plays a crucial role as the primary source of water for various purposes including drinking, washing, farming, and manufacturing, and even when not directly used as a drinking water supply, it remains vital to protect due to its ability to carry contaminants and pollutants from the land into lakes and rivers, which constitute a significant percentage of other people's freshwater supply,. and groundwaterIt is almost ubiquitous underground, residing in the spaces between particles of rock and soil or within crevices and cracks in rock, typically within {{cvt|100 metres|m|ft}} of the surface,<ref name=":0" /> and [[soil]] moisture, and less than 0.01% of it as [[surface water]] in [[lake]]s, [[swamp]]s and [[river]]s.<ref>[http://ga.water.usgs.gov/edu/earthwherewater.html Where is Earth's water?] {{webarchive|url=https://web.archive.org/web/20131214091601/http://ga.water.usgs.gov/edu/earthwherewater.html |date=14 December 2013 }}, [[United States Geological Survey]].</ref><ref>[http://www.physicalgeography.net/fundamentals/8b.html Physicalgeography.net] {{webarchive|url=https://web.archive.org/web/20160126072955/http://www.physicalgeography.net/fundamentals/8b.html |date=26 January 2016 }}. Physicalgeography.net. Retrieved on 29 December 2012.</ref>
Freshwater lakes contain about 87% of this fresh surface water, including 29% in the [[African Great Lakes]], 22% in [[Lake Baikal]] in Russia, 21% in the [[North American Great Lakes]], and 14% in other lakes. Swamps have most of the balance with only a small amount in rivers, most notably the [[Amazon River]]. The atmosphere contains 0.04% water.<ref>{{cite book |last= Gleick |first= Peter |author-link=Peter Gleick|editor= Stephen H. Schneider |title= Encyclopedia of Climate and Weather|url= https://archive.org/details/encyclopediaofcl02schn |url-access= registration |publisher= Oxford University Press |year= 1996|display-authors=etal}}</ref> In areas with no fresh water on the ground surface, fresh water derived from [[precipitation (meteorology)|precipitation]] may, because of its lower density, overlie saline ground water in lenses or layers. Most of the world's fresh water is frozen in [[ice sheet]]s. Many areas have very little fresh water, such as [[desert]]s.
== Freshwater ecosystems ==