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Topic: Aquifer oases

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Oasis

Siwa Oasis

Spring (water)

	Encyclopedia: Aquifer
		Aquifers are typically saturated regions of the subsurface which produce an economically feasible quantity of water to a well or spring (e.g., sand and gravel or fractured bedrock often make good aquifer materials).
		Unconfined aquifers usually receive recharge water directly from the surface, from precipitation or from a body of surface water (e.g., a river, stream, or lake) which is in hydraulic connection with it.
		Aquifers that provide sustainable fresh groundwater to urban areas and for agricultural irrigation are typically close to the ground surface (within a couple of hundred meters) and have some recharge by fresh water.
	www.nationmaster.com /encyclopedia/Aquifer (3362 words)

	Groundwater - Wikipédia
		It is found in aquifers, in the pore spaces of rocks, in unconsolidated sediments, as permafrost, and as soil moisture.
		Groundwater is often contained in aquifers, which are subterranean areas (or layers) of porous material that channel the groundwater's flow.
		Thus the aquifer is permanently reduced in capacity, and the surface of the ground may also subside.
	su.wikipedia.org /wiki/Groundwater (628 words)

	aquifer - Hutchinson encyclopedia article about aquifer (Site not responding. Last check: 2007-09-10)
		The rock of an aquifer must be porous and permeable (full of interconnected holes) so that it can conduct water.
		Aquifers are an important source of fresh water, for example for drinking and irrigation, in many arid areas of the world, and are exploited by the use of artesian wells.
		An aquifer may be underlain, overlain, or sandwiched between less permeable layers, called aquicludes or aquitards, which impede water movement.
	encyclopedia.farlex.com /aquifer (142 words)

	Aquifer oases - Hutchinson encyclopedia article about Aquifer oases (Site not responding. Last check: 2007-09-10)
		Area of land made fertile by the presence of water near the surface in an otherwise arid region.
		The occurrence of oases affects the distribution of plants, animals, and people in the desert regions of the world.
		This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional.
	encyclopedia.farlex.com /Aquifer+oases (280 words)

	Geology of Death Valley National Park
		Infrequent lush oases which exist in the Park as a result of spring discharge water are in obvious contrast to the dry, often barren landscapes immediately adjacent to wetland habitats.
		Ground water movement through the aquifer is generally from north to south through fractured limestone and volcanic rocks or thick alluvial deposits in the valleys.
		Water that passes through the aquifer and ultimately comes to the surface is expressed as point sources (springs or seeps) or as broad, diffuse discharge areas (playa or alkali-encrusted salt flats).
	wrgis.wr.usgs.gov /parks/deva/ftfur2.html (1303 words)

	Aquifer Definition / Aquifer Research (Site not responding. Last check: 2007-09-10)
		An aquifer is an underground layer of water-bearing permeable rock, or permeable mixtures of unconsolidated materials (gravelGravel is rock that is of a certain size range.
		It is located in aquifers, in the pore spaces of rocks, in unconsolidated sediments, as permafrost, and as soil moisture.
		The study of water flow in aquifers and the characterization of aquifers is hydrogeologyHydrogeology (hydro- meaning water, and -geology meaning the study of rocks) is the part of hydrology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in Aquifers).
	www.elresearch.com /Aquifer (623 words)

	Section 10
		If the perched aquifer is located on a hill, there may be spring discharge where water table meets the surface.
		Oases in the North African deserts are artesian springs, which have risen where one of the giant aquifers is breached because of anticlinal folds or faulting as shown in Figure 1.9.5.
		This suggests that the groundwater is large aquifers is of considerable age and may have serious considerations with regard to abstraction.
	pasture.ecn.purdue.edu /~h2o/COURSES/1/section9.htm (794 words)

	Glossary
		Aquifers are vital sources of drinking water in most countries of the world.
		When aquifers are over used then the water is 'mined' and they will have a limited useful life before they dry up.
		The water may seep into the aquifer where the rock is exposed in hills, but because it is confined between watertight layers, it has no means of escape.
	www.curriculumvisions.com /UK/water/waterGlossary.html (1488 words)

	Managing water for peace in the Middle East (Site not responding. Last check: 2007-09-10)
		The apparent age of a groundwater sample, taken from a certain depth in an aquifer, is not influenced only by the flow time of the groundwater particle from the recharge area; to a large extent it is the result of diffusive and convective processes in the aquifer and of mixing within the well.
		Aquifers in the Arabian peninsula are found in arenaceous and/or carbonate formations, including the major formations Saq, Disi, Tabuk, and Wajid of Palaeozoic age; Minjur, Dhruma, Biyadh, and Wasia of Mesozoic age; and Umm er Radhuma and Damman of the Tertiary period (fig.
		The life of the Nubian sandstone aquifer is estimated to be between 20 and 200 years, owing to the lack of data for estimating groundwater recharge through the wadi beds and/or the depressions during occasional and temporary flash floods.
	www.unu.edu /unupress/unupbooks/80858e/80858E08.htm (4735 words)

	[No title]
		In the arid southwestern deserts, all subsurface aquifers are constantly maintained at required levels, as are all streams, lakes and rivers necessary for agricultural and recreational purposes.
		In the deserts, oases have been created and in marshlands water is always available for wildlife.
		Aquifer draw-down may be accompanied by drying and mineral filling of the reservoir pores and cracks.
	www.aapg.org /explorer/2004/08aug/commentary.cfm (543 words)

	ACROSS Final Open Seminar
		Phreatic aquifers are presently causing serious problems to the local public authorities and especially to the water resources managers.
		The CI extends across the Algerian-Tunisian border and the principal areas of recharge are in the South Atlas Mountains of Algeria and Tunisia and the Dahar mountains of Tunisia.
		The aquifer is bounded by more saline waters in the formations above and below, as well as in the discharge area of the Chotts and therefore the waters are vulnerable to pollution through increased salinity caused by over-pumping which would induce excessive drawdowns.
	www.diam.unige.it /~idromet/avi080/part-sem/moulla.htm (1012 words)

	Groundwater
		The aquifer of this artesian system, the Dakota Sandstone, is recharged where it is exposed along the margins of the Black Hills of South Dakota.
		Irrigation from the High Plains aquifer is largely responsible for the high agricultural productivity of this region, where a significant percentage of the nation’s corn, cotton, and wheat is grown, and half of U.S. beef cattle are raised.
		Consequently, water is being removed from the aquifer faster than it is being replenished, causing the water table to drop significantly in many areas.
	blank005.tripod.com /geology/groundwater.html (6376 words)

	Guidelines for the management of groundwater (Site not responding. Last check: 2007-09-10)
		Upward flow of water from the aquifer to the wetland is termed groundwater discharge and downward from the wetland to the aquifer is called groundwater recharge (Figure 4).
		the aquifer discharges to the wetland (Fariz and Hatough-Bouran 1998).
		Especially in the case where wetlands are associated with large regional aquifers, whose boundaries may extend beyond the watershed, it is necessary to monitor the status of the groundwater resource and demands on groundwater, concurrently with monitoring of the status and response of wetlands to changes in groundwater availability.
	www.ramsar.org /cop9_dr01_annexcii_e.htm (10679 words)

	Hydrologic Reality: International Water Law and Transboundary Ground-Water Resources
		Watertable or unconfined aquifers are aquifers whose watertable (top boundary of the aquifer) are generally found relatively close to the land surface, and which contain layers of materials of high permeability extending from the land surface to the impermeable base of the aquifer.
		Consequently, any scheme designed to exploit or manage the aquifer by one or more of the four nations sharing the resource would be exempt from abiding by the principles contained in the Convention, regardless of the potential or actual consequences to the quality or quantity of the water in the aquifer.
		The Judean Mountain aquifer is an unconfined aquifer in the highlands, and a confined aquifer along the westward and eastern slopes.
	www.internationalwaterlaw.org /Articles/GlobalSouth.htm (3716 words)

	What are Playa Lakes? (Site not responding. Last check: 2007-09-10)
		The majority of playa lakes are located in or adjacent to farms, grazing lands and feedlots, which can create a number of impacts on playas including: pesticide and fertilizer runoff, contaminants from feedlot runoff, overgrazing and sedimentation.
		Studies have found that water in playas percolates underground from basin edges into the Ogallala Aquifer - a 174,000 square-mile formation spanning sections of eight states, including all six of the PLJV region.
		The Aquifer is an important resource for farmers, many of who pump water from it for irrigation.
	www.pljv.org /whatare.html (607 words)

	Presentation
		EgyptIn general terms, the main goal of sustainable groundwater and aquifer management should be to maintain the long-term balance of the system, including both the groundwater resource (in terms of quantity and quality), the ecology and human welfare.
		Sustainable groundwater and aquifer management was defined as utilizing water in a wise way, in order to sustain the yields of the water sources in quantity and quality, taking into consideration future generation rights in these resources.
		Worth mentioning here are shared aquifers and groundwater bodies between nations, where actions should be applied for an aquifer or for a groundwater body as a whole.
	info.worldbank.org /etools/bspan/PresentationView.asp?PID=237&EID=121 (2744 words)

	Station Information - Water table (Site not responding. Last check: 2007-09-10)
		A large amount of water below the ground table is called an aquifer.
		Springs and oases occur when the water table reaches the surface.
		The practice of drilling wells to extract groundwater is dependent on the water table.
	www.stationinformation.com /encyclopedia/w/wa/water_table.html (82 words)

	World War 1 and 2 - Water table
		A so-called "perched aquifer" (or perched water table) occurs when the descent of water percolating from above is blocked by a shelf of impermeable rock.
		The porous media in which groundwaters occur are the complex geologic materials near the earth surface; hence local details of porosity and permeability are as complex as those materials.
		Generally, the more productive and useful aquifers are in sedimentary geologic formations, though weathered and fractured crystalline rocks yield smaller volumes of groundwater in many environments.
	www.worldwardiary.com /history/Watertable (395 words)

	AQUASTAT - FAO's Information System on Water and Agriculture (Site not responding. Last check: 2007-09-10)
		The total area can be divided into 4 571 ha of oases and 44 629 ha of schemes in the provinces of the valley of the Senegal river and its tributaries.
		There are 31 400 wells in the oases, in the majority of which the water is extracted manually.
		About 400 000 people live in the oases, but only 14 700 families possess the 4 751 ha of palm trees (more than one million productive palm trees) and cultivate around 244 ha of annual crops under the palm trees.
	www.fao.org /ag/agl/aglw/aquastat/countries/mauritania/print1.stm (1111 words)

	Geology 101 - Lecture Key Points (Site not responding. Last check: 2007-09-10)
		Groundwater flows through the ground by way of aquifers, water-transmitting layers of rocks or sediment (these are permeable).
		When an aquifer is "tilted", the water within it develops pressure that enables it to flow out of the ground under pressure - a so-called artesian aquifer (self-pumping).
		When too much freshwater is pumped out of aquifers, seawater invades the aquifer and municipal water may become saltwater.
	staff.washington.edu /sechern/ess101/key/030310.html (212 words)

	NPCA Destination Finder
		Several of the larger Death Valley springs derive their water from a regional aquifer which extends as far east as southern Nevada and Utah.
		Much of the water drawn from this aquifer was charged many thousands of years ago, during the Pleistocene ice ages, when climate was cooler and wetter.
		Today's drier climate does not provide enough precipitation to recharge the aquifer at the rate at which water is being withdrawn.
	syndication.getoutdoors.com /npca/destination_description/15.html (300 words)

	History
		Creatures living in and near playas are well adapted to the wet and dry cycles of playa lakes, which are oases in the Southern High Plains of not only water, but of habitat, as well.
		The Ogallala aquifer underlying the SHP is the largest aquifer in the world.
		It is named for the Oglala Sioux who reside in western Nebraska, near the northern-most reach of the aquifer.
	www.rw.ttu.edu /ppna/history.htm (1061 words)

	biology - Groundwater
		It is estimated that groundwater is fifty times that of surface freshwater[1].
		The top of the upper unconfined aquifer is called the water table or phreatic groundwater, where water pressure is equal to atmospheric pressure.
		The region between the land surface and the water table is called the unsaturated or vadose zone ("vadose" is Latin for "shallow").
	biologydaily.com /biology/Groundwater (720 words)

	Etymological Conduit to the Land of Qanat by Dr. V. Sankaran Nair
		Qanat is an ancient system found in arid regions that bring groundwater from the cliff, or base of a mountainous area, following a water-bearing formation (aquifer) or rarely from rivers, and emerge at an oasis, through underground tunnel or a series of tunnels.
		First settlers who lived in the natural oases might have developed the idea of qanat to bring other arid but fertile terrain under cultivation and sustain their life.
		The aflaj have helped to shape the history and settlement patterns of oases, and they continue even now binding together each community that draws upon the water form the falaj.
	www.boloji.com /environment/24.htm (2670 words)

	Niger designates five Ramsar sites
		A complex of permanent and temporary streams, oases and marshes at the centre of the Niger portion of the Sahara desert, hosting a number of endangered species such as the vulnerable cheetah, Barbary sheep and Dorcas gazelle, as well as the critically endangered Addax.
		The oases are part of the enormous aquifer system of the Djado and Bilma basins and are fed by freshwater resurgence and a shallow water table.
		This water source is essential for the local population, which practices subsistence agriculture in small fields around the oases, growing vegetables (peanuts, salad, cabbage, carrots) and fruits (guava, mangoes, citrus and bananas) which contribute to families' income.
	www.ramsar.org /wn/w.n.niger_four.htm (1168 words)

	Science Serving People
		Though the aquifer supports dreams of blooming deserts, unrestricted steps to exploit it could lead to nightmares if not taken carefully.
		Oases born decades ago are home to thousands of farming families, and wells have been drilled for irrigation and residential needs.
		The analysts are using sensitive isotope techniques that enable them to analyze underground water molecules they cannot see but can draw to the surface and sample.
	www.iaea.org /Publications/Booklets/Ssp/great_lakes.html (1055 words)

	Al-Ahram Weekly \| Travel \| Ten green feddans (Site not responding. Last check: 2007-09-10)
		Underneath Farafra, the remotest of the four oasis of the New Valley from the Nile, lie deep aquifers of mineral-rich water.
		They drew up plans to flood the oases with both immigrants and irrigation channels and cultivate half a million feddans, producing enough food to feed a sizeable chunk of the country's growing population.
		Water to farmers on the project is rationed according to crop, and is turned off on occasion -- as, for example, during the Eid, when it is understood that no one will bother to go to the fields and use the irrigation system correctly.
	weekly.ahram.org.eg /2002/574/tr2.htm (1805 words)

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