Aquifer - Revision history

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	[[Category: Done ~~2015~~-09-06]]		[[Category:Done 2017-07-01]]
	<onlyinclude>An '''aquifer''' is a [[porosity\|porous]], water-saturated layer of sand, gravel, or bedrock, which contains [[groundwater]] or has [[material flow\|flowing]] groundwater. They are accessible by a well, and provide the world with around 1/4 of its drinking [[water]].</onlyinclude><ref name=hackett>G. Tyler Miller, Jr. and D. Hackett, "Water Resources," in ''Living in the Environment'', 2nd ed. USA: Nelson , 2011, ch.15, pp.323-349</ref> ~~They are located beneath a~~ water ~~table (the border between~~ the ~~zone saturated with~~ water and the ~~zone that is not~~) ~~and above water-tight layers~~ of ~~rock which prevent the water from seeping out~~.		<onlyinclude>An '''aquifer''' is a [[porosity\|porous]], water-saturated layer of sand, gravel, or bedrock, which contains [[groundwater]] or has [[material flow\|flowing]] groundwater. Simply put, aquifers are large, underground stores of water. They are accessible by a well, and provide the world with around 1/4 of its drinking [[water]].</onlyinclude><ref name=hackett>G. Tyler Miller, Jr. and D. Hackett, "Water Resources," in ''Living in the Environment'', 2nd ed. USA: Nelson , 2011, ch.15, pp.323-349</ref> The upper level of the underground water is called the water table.<ref name=RE1>U. Howard Perlman, "Aquifers and Groundwater, from USGS Water-Science School", Water.usgs.gov, 2016. [Online]. Available: http://water.usgs.gov/edu/earthgwaquifer.html. [Accessed: 09- Jun- 2016].</ref> The world's largest known aquifer is the Great Artesian Basin, in Australia, at more than 1.7 million square kilometers.<ref name=RE4>Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.</ref>

	Aquifers are sorted into unconfined and confined aquifers:<ref name=hackett/>		Aquifers are sorted into unconfined and confined aquifers:<ref name=hackett/>

	*'''Unconfined aquifers''' have a layer of [[permeability~~\|impermeable~~]] rock below them, ~~but~~ are ~~not~~ bounded on the top. This means they are ~~not~~ under [[pressure]]~~, and require the use of a [[pump]] to lift out the water~~.		*'''Unconfined aquifers''' have a layer of low [[permeability]] rock or sediment below them, and are bounded on the top by the water table. Since they do not have a low permeability confining layer above them they are termed unconfined. This means they are generally found closer to the ground surface and under lower [[pressure]].

	*'''Confined aquifers''' are ~~confined on~~ both the ~~top and bottom by impermeable~~ rock, in ~~which~~ the water is ~~often under high~~ pressure and ~~can flow~~ to the surface ~~naturally upon~~ the ~~drilling~~ of a well.<ref name=~~usgs~~/>		*'''Confined aquifers''' are aquifers which have surrounding rock both above and below the porous rock, confining the pressure in the porous rock and its water.<ref name=RE1/> This causes a well to become pressurized. If a well is drilled into this confined "pressurized" aquifer, the internal pressure can be enough to push the water up the well and up to the surface without the aid of a pump, sometimes completely out of the well. This type of well is called artesian.<ref name=RE1/>

			Rocks that encompass freshwater have been discovered at depths of more than 1829 m and salty water has come from oil wells at depths of more than 9144 m.<ref name=RE1/> However, on average the porosity and permeability of rocks decrease as their depth below land surface increases. This is because the pores and cracks in rocks which are at high depths are closed or greatly reduced in size because of the weight of rocks above.<ref name=RE1/>
			Fractured volcanic rocks such as columnar basalts also make good aquifers.<ref name=RE2>"What is an Aquifer?", Imnh.isu.edu, 2016. [Online]. Available: http://imnh.isu.edu/digitalatlas/hydr/concepts/gwater/aquifer.htm. [Accessed: 09- Jun- 2016].</ref> Rocks such as granite and schist are generally poor aquifers because they have a very low porosity.<ref name=RE2/>

	Aquifers are replenished naturally by [[precipitation]], which is known as '''~~natural~~ recharge'''. Some can be recharged by stream [[run-off]]~~, which is known as '''lateral~~ recharge~~'''. These processes can occur~~ extremely slowly, with ~~water typically flowing downwards at~~ about 1 [[meter]] or so per [[year]] and ~~rarely faster~~ than 0.3 meters (a ~~[[foot]]) a day~~.<ref name=hackett/> If the ~~drawing~~ of ~~water~~ is done slower than it naturally replenishes, then the aquifer is a renewable source of water.		Aquifers are replenished naturally by [[precipitation]], which is known as '''groundwater recharge'''. However, the rate of recharge is not the same for all aquifers; this is important to note when pumping water from a well. Pumping too much water at a fast rate decreases the water levels in the aquifer and eventually causes a well to return less and less water and can even run dry. Some aquifers can be recharged laterally by exchanging water with stream [[run off]]. Groundwater recharge occurs extremely slowly, with rates of groundwater recharge commonly less than about 1 [[meter]] or so per [[year]] and they can be less than 0.1 meters a year in arid regions.<ref name=hackett/> If the extraction of groundwater is done slower than it naturally replenishes, then the aquifer can be a renewable source of water.

	[[File:aquiferimg.png\|600px\|center\|thumb\|Figure 1. A diagram portraying the layout of an aquifer and distinguishing between "confined" and "unconfined".<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/c/c7/Groundwater_flow.svg</ref>]]		[[File:aquiferimg.png\|600px\|center\|thumb\|Figure 1. A diagram portraying the layout of an aquifer and distinguishing between "confined" and "unconfined".<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/c/c7/Groundwater_flow.svg</ref>]]
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	==Concerns==		==Concerns==

	There are many concerns with water use from aquifers and how it may affect local geography and ecosystems. Water is often drawn faster from aquifers than they naturally replenish, especially in agriculture intense countries like China, India and the United States, which results in ~~these~~ resources ~~drying up~~. Withdrawal rates have increased rapidly in the past century, with global water withdrawal increasing sevenfold and [[per capita]] water withdrawal being quadrupled.<Ref name=hackett/>		There are many concerns with water use from aquifers and how it may affect local geography and ecosystems. Water is often drawn faster from aquifers than they naturally replenish, especially in agriculture intense countries like China, India and the United States, which results in a depletion of groundwater resources. Withdrawal rates have increased rapidly in the past century, with global water withdrawal increasing sevenfold and [[per capita]] water withdrawal being quadrupled.<Ref name=hackett/>

	The over-~~drawing~~ of water also results in ~~the water tables~~ falling, meaning that one needs to go deeper to find an aquifer.<ref name=usgs>USGS. (August 12, 2015). ''Aquifers and Groundwater'' [Online], Available: http://water.usgs.gov/edu/earthgwaquifer.html</ref> ~~This is~~ often difficult to see happening so it is generally too late to act until damage is already done. The first sign of this is typically dry wells, followed by a loss of water in deeper wells. This has an effect on [[rural population]]s who rely on the use of aquifers for their water supply, and indirectly increases the gap between the rich and poor in some areas.<Ref name=hackett/>		The over-exploitation of water also results in falling groundwater levels, meaning that one needs to go deeper to find an aquifer.<ref name=usgs>USGS. (August 12, 2015). ''Aquifers and Groundwater'' [Online], Available: http://water.usgs.gov/edu/earthgwaquifer.html</ref> Groundwater level declines are often difficult to see happening so it is generally too late to act until damage is already done. The first sign of this is typically dry wells, followed by a loss of water in deeper wells. This has an effect on [[rural population]]s who rely on the use of aquifers for their water supply, and indirectly increases the gap between the rich and poor in some areas.<Ref name=hackett/> In other cases, such as [[iron]] staining, health impacts due to high concentrations of dissolved iron are not a problem as much as the aesthetic quality of the drinking water supply. In other cases, where elements such as fluoride, [[uranium]], or arsenic occur naturally in high concentrations, human health may be affected.<ref name=RE3>"Groundwater needs protection", Environment and Climate Change Canada, 2016. [Online]. Available: https://www.ec.gc.ca/eau-water/default.asp?lang=En&n=300688DC-1#protection. [Accessed: 07- Jun- 2016].</ref>

	==References==		==References==
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J.williams: 1 revision imported

2015-09-18T16:51:19Z

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Kjstenho at 20:30, 3 September 2015

2015-09-03T20:30:39Z

← Older revision		Revision as of 20:30, 3 September 2015
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	[[Category:Done 2015-08-21]]		[[Category: Done 2015-09-06]]
	<onlyinclude>An '''aquifer''' is a [[porosity\|porous]], water-saturated layer of sand, gravel, or bedrock, which contains [[groundwater]] or has [[material flow\|flowing]] groundwater. They are accessible by a well, and provide the world with around 1/4 of its drinking [[water]].</onlyinclude><ref name=hackett>G. Tyler Miller, Jr. and D. Hackett, "Water Resources," in ''Living in the Environment'', 2nd ed. USA: Nelson , 2011, ch.15, pp.323-349</ref> They are located beneath a water table (the border between the zone saturated with water and the zone that is not) and above water-tight layers of rock which prevent the water from seeping out.		<onlyinclude>An '''aquifer''' is a [[porosity\|porous]], water-saturated layer of sand, gravel, or bedrock, which contains [[groundwater]] or has [[material flow\|flowing]] groundwater. They are accessible by a well, and provide the world with around 1/4 of its drinking [[water]].</onlyinclude><ref name=hackett>G. Tyler Miller, Jr. and D. Hackett, "Water Resources," in ''Living in the Environment'', 2nd ed. USA: Nelson , 2011, ch.15, pp.323-349</ref> They are located beneath a water table (the border between the zone saturated with water and the zone that is not) and above water-tight layers of rock which prevent the water from seeping out.

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	*'''Confined aquifers''' are confined on both the top and bottom by impermeable rock, in which the water is often under high pressure and can flow to the surface naturally upon the drilling of a well.<ref name=usgs/>		*'''Confined aquifers''' are confined on both the top and bottom by impermeable rock, in which the water is often under high pressure and can flow to the surface naturally upon the drilling of a well.<ref name=usgs/>

	Aquifers are replenished naturally by [[precipitation]], which is known as '''natural recharge'''. Some can be recharged by stream [[run-off]], which is known as '''lateral recharge'''. These processes can occur extremely slowly, with water typically flowing downwards at about 1 [[meter]] or so per year and rarely faster than 0.3 meters (a [[foot]]) a day.<ref name=hackett/> If the drawing of water is done slower than it naturally replenishes, then the aquifer is a renewable source of water.		Aquifers are replenished naturally by [[precipitation]], which is known as '''natural recharge'''. Some can be recharged by stream [[run-off]], which is known as '''lateral recharge'''. These processes can occur extremely slowly, with water typically flowing downwards at about 1 [[meter]] or so per [[year]] and rarely faster than 0.3 meters (a [[foot]]) a day.<ref name=hackett/> If the drawing of water is done slower than it naturally replenishes, then the aquifer is a renewable source of water.

	[[File:aquiferimg.png\|600px\|center\|thumb\|Figure 1. A diagram portraying the layout of an aquifer and distinguishing between "confined" and "unconfined".<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/c/c7/Groundwater_flow.svg</ref>]]		[[File:aquiferimg.png\|600px\|center\|thumb\|Figure 1. A diagram portraying the layout of an aquifer and distinguishing between "confined" and "unconfined".<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/c/c7/Groundwater_flow.svg</ref>]]

J.williams: 1 revision imported

2015-08-26T21:31:50Z

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J.williams at 18:50, 24 August 2015

2015-08-24T18:50:34Z

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[[Category:Done 2015-08-21]]
<onlyinclude>An '''aquifer''' is a [[porosity|porous]], water-saturated layer of sand, gravel, or bedrock, which contains [[groundwater]] or has [[material flow|flowing]] groundwater. They are accessible by a well, and provide the world with around 1/4 of its drinking [[water]].</onlyinclude><ref name=hackett>G. Tyler Miller, Jr. and D. Hackett, "Water Resources," in ''Living in the Environment'', 2nd ed. USA: Nelson , 2011, ch.15, pp.323-349</ref> They are located beneath a water table (the border between the zone saturated with water and the zone that is not) and above water-tight layers of rock which prevent the water from seeping out.

Aquifers are sorted into unconfined and confined aquifers:<ref name=hackett/>

*'''Unconfined aquifers''' have a layer of [[permeability|impermeable]] rock below them, but are not bounded on the top. This means they are not under [[pressure]], and require the use of a [[pump]] to lift out the water.

*'''Confined aquifers''' are confined on both the top and bottom by impermeable rock, in which the water is often under high pressure and can flow to the surface naturally upon the drilling of a well.<ref name=usgs/>

Aquifers are replenished naturally by [[precipitation]], which is known as '''natural recharge'''. Some can be recharged by stream [[run-off]], which is known as '''lateral recharge'''. These processes can occur extremely slowly, with water typically flowing downwards at about 1 [[meter]] or so per year and rarely faster than 0.3 meters (a [[foot]]) a day.<ref name=hackett/> If the drawing of water is done slower than it naturally replenishes, then the aquifer is a renewable source of water.

[[File:aquiferimg.png|600px|center|thumb|Figure 1. A diagram portraying the layout of an aquifer and distinguishing between "confined" and "unconfined".<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/c/c7/Groundwater_flow.svg</ref>]]

==Concerns==

There are many concerns with water use from aquifers and how it may affect local geography and ecosystems. Water is often drawn faster from aquifers than they naturally replenish, especially in agriculture intense countries like China, India and the United States, which results in these resources drying up. Withdrawal rates have increased rapidly in the past century, with global water withdrawal increasing sevenfold and [[per capita]] water withdrawal being quadrupled.<Ref name=hackett/>

The over-drawing of water also results in the water tables falling, meaning that one needs to go deeper to find an aquifer.<ref name=usgs>USGS. (August 12, 2015). ''Aquifers and Groundwater'' [Online], Available: http://water.usgs.gov/edu/earthgwaquifer.html</ref> This is often difficult to see happening so it is generally too late to act until damage is already done. The first sign of this is typically dry wells, followed by a loss of water in deeper wells. This has an effect on [[rural population]]s who rely on the use of aquifers for their water supply, and indirectly increases the gap between the rich and poor in some areas.<Ref name=hackett/>

==References==
{{Reflist}}[[Category:Uploaded]]