What force pushes groundwater from pore to pore below the water table? *

Surreptitious layer of h2o-bearing permeable rock

An aquifer is an underground layer of water-bearing permeable stone, stone fractures or unconsolidated materials (gravel, sand, or silt).

Groundwater from aquifers can be extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability forth an aquifer,^[one] and aquiclude (or aquifuge), which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could create a confined aquifer.

Aquifers can be classified as follows: saturated versus unsaturated; aquifers versus aquitards; bars versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer. Challenges for the uses of groundwater from aquifers include: subsidence, saltwater intrusion, salination and groundwater pollution.

Depth [edit]

An aquifer cross-section. This diagram shows two aquifers with one aquitard (a confining or impermeable layer) between them, surrounded by the bedrock aquiclude, which is in contact with a gaining stream (typical in humid regions). The water table and unsaturated zone are likewise illustrated.

Aquifers occur from near-surface to deeper than ix,000 metres (30,000 ft).^[2] Those closer to the surface are non just more than likely to be used for water supply and irrigation, merely are also more than likely to be replenished by local rainfall. Although aquifers are sometimes characterized as "underground rivers or lakes," they are actually porous rock saturated with water.^[iii]

Many desert areas take limestone hills or mountains inside them or close to them that can be exploited as groundwater resources. Role of the Atlas Mountains in North Africa, the Lebanon and Anti-Lebanon ranges between Syria and Lebanon, the Jebel Akhdar in Sultanate of oman, parts of the Sierra Nevada and neighboring ranges in the United States' Southwest, take shallow aquifers that are exploited for their water. Overexploitation can lead to the exceeding of the practical sustained yield; i.e., more water is taken out than can be replenished.

Along the coastlines of certain countries, such every bit Libya and Israel, increased water usage associated with population growth has caused a lowering of the water tabular array and the subsequent contamination of the groundwater with saltwater from the body of water.

In 2013 large freshwater aquifers were discovered under continental shelves off Australia, China, Northward America and South Africa. They contain an estimated half a million cubic kilometers of "low salinity" water that could be economically processed into potable water. The reserves formed when ocean levels were lower and rainwater made its way into the basis in land areas that were not submerged until the ice age ended 20,000 years agone. The volume is estimated to be 100 times the corporeality of water extracted from other aquifers since 1900.^{[iv] [five]}

Nomenclature [edit]

An aquitard is a zone within the Earth that restricts the flow of groundwater from one aquifer to another. An aquitard can sometimes, if completely impermeable, be called an aquiclude or aquifuge. Aquitards are equanimous of layers of either clay or non-porous rock with low hydraulic conductivity.

Saturated versus unsaturated [edit]

Groundwater tin can be found at nigh every signal in the World's shallow subsurface to some degree, although aquifers exercise not necessarily contain fresh water. The Earth'south crust can be divided into two regions: the saturated zone or phreatic zone (eastward.g., aquifers, aquitards, etc.), where all available spaces are filled with water, and the unsaturated zone (also called the vadose zone), where there are notwithstanding pockets of air that contain some water, but tin can exist filled with more water.

Saturated means the pressure head of the water is greater than atmospheric force per unit area (it has a gauge pressure level > 0). The definition of the h2o table is the surface where the pressure head is equal to atmospheric pressure (where gauge force per unit area = 0).

Unsaturated conditions occur to a higher place the water table where the pressure caput is negative (absolute pressure tin never exist negative, but gauge pressure can) and the water that incompletely fills the pores of the aquifer material is under suction. The water content in the unsaturated zone is held in place by surface adhesive forces and it rises above the h2o table (the zero-judge-pressure isobar) by capillary action to saturate a small-scale zone above the phreatic surface (the capillary fringe) at less than atmospheric pressure. This is termed tension saturation and is not the same equally saturation on a water-content ground. Water content in a capillary fringe decreases with increasing distance from the phreatic surface. The capillary head depends on soil pore size. In sandy soils with larger pores, the head will be less than in clay soils with very minor pores. The normal capillary rising in a clayey soil is less than 1.8 m (vi ft) simply can range between 0.3 and 10 m (ane and 33 ft).^[six]

The capillary rising of h2o in a small-bore tube involves the aforementioned physical procedure. The h2o table is the level to which water will rise in a large-diameter piping (e.g., a well) that goes down into the aquifer and is open up to the atmosphere.

Aquifers versus aquitards [edit]

Aquifers are typically saturated regions of the subsurface that produce an economically feasible quantity of water to a well or jump (e.k., sand and gravel or fractured bedrock frequently make skilful aquifer materials).

An aquitard is a zone inside the Earth that restricts the flow of groundwater from one aquifer to another. A completely impermeable aquitard is chosen an aquiclude or aquifuge. Aquitards contain layers of either clay or non-porous rock with low hydraulic conductivity.

In mountainous areas (or near rivers in mountainous areas), the chief aquifers are typically unconsolidated alluvium, composed of mostly horizontal layers of materials deposited by water processes (rivers and streams), which in cross-section (looking at a 2-dimensional piece of the aquifer) appear to be layers of alternating fibroid and fine materials. Fibroid materials, because of the high energy needed to motility them, tend to be found nearer the source (mountain fronts or rivers), whereas the fine-grained fabric volition make information technology farther from the source (to the flatter parts of the basin or overbank areas—sometimes called the force per unit area area). Since in that location are less fine-grained deposits most the source, this is a identify where aquifers are often unconfined (sometimes called the forebay expanse), or in hydraulic advice with the land surface.

Bars versus unconfined [edit]

There are two end members in the spectrum of types of aquifers; bars and unconfined (with semi-confined beingness in between). Unconfined aquifers are sometimes also called h2o table or phreatic aquifers, considering their upper purlieus is the h2o tabular array or phreatic surface. (See Biscayne Aquifer.) Typically (simply not always) the shallowest aquifer at a given location is unconfined, meaning it does not have a confining layer (an aquitard or aquiclude) betwixt it and the surface. The term "perched" refers to ground water accumulating higher up a low-permeability unit or strata, such as a clay layer. This term is generally used to refer to a small local area of ground h2o that occurs at an top higher than a regionally extensive aquifer. The difference between perched and unconfined aquifers is their size (perched is smaller). Confined aquifers are aquifers that are overlain by a circumscribed layer, often made upward of clay. The confining layer might offer some protection from surface contamination.

If the stardom between confined and unconfined is not clear geologically (i.east., if it is not known if a clear confining layer exists, or if the geology is more circuitous, east.g., a fractured boulder aquifer), the value of storativity returned from an aquifer test can exist used to determine it (although aquifer tests in unconfined aquifers should be interpreted differently than confined ones). Confined aquifers have very low storativity values (much less than 0.01, and as trivial equally 10 ⁻⁵ ), which means that the aquifer is storing water using the mechanisms of aquifer matrix expansion and the compressibility of water, which typically are both quite small quantities. Unconfined aquifers accept storativities (typically chosen specific yield) greater than 0.01 (1% of bulk volume); they release water from storage by the machinery of actually draining the pores of the aquifer, releasing relatively large amounts of water (upward to the drainable porosity of the aquifer cloth, or the minimum volumetric water content).

Isotropic versus anisotropic [edit]

In isotropic aquifers or aquifer layers the hydraulic conductivity (Chiliad) is equal for flow in all directions, while in anisotropic conditions it differs, notably in horizontal (Kh) and vertical (Kv) sense.

Semi-confined aquifers with one or more aquitards work as an anisotropic arrangement, fifty-fifty when the separate layers are isotropic, because the compound Kh and Kv values are different (see hydraulic transmissivity and hydraulic resistance).

When calculating period to drains^[7] or flow to wells^[8] in an aquifer, the anisotropy is to exist taken into account lest the resulting design of the drainage system may exist faulty.

Porous, karst, or fractured [edit]

To properly manage an aquifer its backdrop must be understood. Many properties must be known to predict how an aquifer will respond to rainfall, drought, pumping, and contamination. Where and how much water enters the groundwater from rainfall and snowmelt? How fast and what direction does the groundwater travel? How much water leaves the basis as springs? How much water tin can be sustainably pumped out? How quickly will a contagion incident achieve a well or spring? Computer models can exist used to test how accurately the agreement of the aquifer backdrop matches the actual aquifer performance.^{[nine] : 192–193, 233–237} Environmental regulations require sites with potential sources of contamination to demonstrate that the hydrology has been characterized.^{[ix] : 3}

Porous [edit]

Water in porous aquifers slowly seeps through pore spaces between sand grains

Porous aquifers typically occur in sand and sandstone. Porous aquifer properties depend on the depositional sedimentary environment and later on natural cementation of the sand grains. The surround where a sand body was deposited controls the orientation of the sand grains, the horizontal and vertical variations, and the distribution of shale layers. Fifty-fifty sparse shale layers are important barriers to groundwater flow. All these factors touch the porosity and permeability of sandy aquifers.^{[x] : 413}

Sandy deposits formed in shallow marine environments and in windblown sand dune environments accept moderate to high permeability while sandy deposits formed in river environments have low to moderate permeability.^{[10] : 418} Rainfall and snowmelt enter the groundwater where the aquifer is near the surface. Groundwater flow directions tin can be determined from potentiometric surface maps of h2o levels in wells and springs. Aquifer tests and well tests can be used with Darcy'due south law flow equations to determine the power of a porous aquifer to convey water.^{[nine] : 177–184}

Analyzing this type of information over an area gives an indication how much water can be pumped without overdrafting and how contamination volition travel.^{[9] : 233} In porous aquifers groundwater flows as tiresome seepage in pores betwixt sand grains. A groundwater flow rate of ane human foot per twenty-four hour period (0.three m/d) is considered to exist a high rate for porous aquifers,^[11] as illustrated by the water slowly seeping from sandstone in the accompanying image to the left.

Porosity is important, merely, lonely, information technology does not make up one's mind a rock's ability to act every bit an aquifer. Areas of the Deccan Traps (a basaltic lava) in west primal India are skilful examples of rock formations with high porosity simply low permeability, which makes them poor aquifers. Similarly, the micro-porous (Upper Cretaceous) Chalk Group of s east England, although having a reasonably loftier porosity, has a low grain-to-grain permeability, with its skilful water-yielding characteristics generally due to micro-fracturing and fissuring.

Karst [edit]

H2o in karst aquifers flows through open conduits where h2o flows as underground streams

Karst aquifers typically develop in limestone. Surface h2o containing natural carbonic acid moves downward into small fissures in limestone. This carbonic acid gradually dissolves limestone thereby enlarging the fissures. The enlarged fissures allow a larger quantity of water to enter which leads to a progressive enlargement of openings. Abundant small openings store a big quantity of water. The larger openings create a conduit organization that drains the aquifer to springs.^[12]

Characterization of karst aquifers requires field exploration to locate sinkholes, swallets, sinking streams, and springs in addition to studying geologic maps.^{[13] : four} Conventional hydrogeologic methods such as aquifer tests and potentiometric mapping are insufficient to characterize the complication of karst aquifers. These conventional investigation methods need to exist supplemented with dye traces, measurement of bound discharges, and analysis of water chemical science.^[14] U.Southward. Geological Survey dye tracing has adamant that conventional groundwater models that assume a uniform distribution of porosity are non applicative for karst aquifers.^[xv]

Linear alignment of surface features such as direct stream segments and sinkholes develop along fracture traces. Locating a well in a fracture trace or intersection of fracture traces increases the likelihood to encounter good water production.^[16] Voids in karst aquifers tin be large enough to cause destructive collapse or subsidence of the ground surface that can create a catastrophic release of contaminants.^{[9] : 3–4} Groundwater catamenia charge per unit in karst aquifers is much more rapid than in porous aquifers as shown in the accompanying image to the left. For instance, in the Barton Springs Edwards aquifer, dye traces measured the karst groundwater flow rates from 0.v to 7 miles per day (0.8 to xi.3 km/d).^[17] The rapid groundwater flow rates make karst aquifers much more than sensitive to groundwater contamination than porous aquifers.^{[13] : one}

In the farthermost case, groundwater may exist in hugger-mugger rivers (e.g., caves underlying karst topography.

Fractured [edit]

If a rock unit of low porosity is highly fractured, it can besides make a practiced aquifer (via fissure flow), provided the rock has a hydraulic conductivity sufficient to facilitate move of water.

Transboundary aquifer [edit]

Map of major US aquifers past stone type

When an aquifer transcends international boundaries, the term transboundary aquifer applies.^[18]

Transboundariness is a concept, a measure out and an arroyo first introduced in 2017.^[xix] The relevance of this approach is that the concrete features of the aquifers become simply additional variables amongst the broad spectrum of considerations of the transboundary nature of an aquifer:

• social (population);
• economic (groundwater productivity);
• political (as transboundary);
• bachelor research or information;
• water quality and quantity;
• other problems governing the agenda (security, trade, immigration and and so on).

The discussion changes from the traditional question of "is the aquifer transboundary?" to "how transboundary is the aquifer?".

The socio-economic and political contexts effectively overwhelm the aquifer'due south physical features calculation its corresponding geostrategic value (its transboundariness)^[20]

The criteria proposed by this arroyo endeavor to encapsulate and mensurate all potential variables that play a role in defining the transboundary nature of an aquifer and its multidimensional boundaries.

Human apply of groundwater [edit]

About land areas on Earth have some form of aquifer underlying them, sometimes at significant depths. In some cases, these aquifers are rapidly being depleted by the man population.

Of all natural resource, groundwater is the most extracted resource in the world. As of 2010, the tiptop five countries past volume of groundwater extraction were India, China, the U.s., Pakistan, and Islamic republic of iran. A majority of extracted groundwater, seventy%, is used for agricultural purposes.^[21] Groundwater is the near accessed source of freshwater around the world, including equally drinking water, irrigation, and manufacturing. Groundwater accounts for nigh half of the world's drinking h2o, 40% of its irrigation h2o, and a 3rd of water for industrial purposes.^[22]

Fresh-water aquifers, especially those with limited recharge by snow or rain, as well known as meteoric water, can be over-exploited and depending on the local hydrogeology, may depict in non-potable water or saltwater intrusion from hydraulically connected aquifers or surface water bodies. This can exist a serious trouble, particularly in coastal areas and other areas where aquifer pumping is excessive. In some areas, the ground water tin become contaminated by arsenic and other mineral poisons.

Aquifers are critically important in homo dwelling and agriculture. Deep aquifers in arid areas have long been h2o sources for irrigation (see Ogallala below). Many villages and even large cities depict their water supply from wells in aquifers.

Challenges for uses of aquifers [edit]

Subsidence [edit]

In unconsolidated aquifers, groundwater is produced from pore spaces between particles of gravel, sand, and silt. If the aquifer is confined by low-permeability layers, the reduced h2o pressure level in the sand and gravel causes slow drainage of h2o from the adjoining confining layers. If these confining layers are equanimous of compressible silt or clay, the loss of h2o to the aquifer reduces the h2o pressure in the confining layer, causing it to compress from the weight of overlying geologic materials. In severe cases, this compression can be observed on the ground surface every bit subsidence. Unfortunately, much of the subsidence from groundwater extraction is permanent (elastic rebound is small). Thus, the subsidence is not only permanent, but the compressed aquifer has a permanently reduced capacity to agree h2o.

Saltwater intrusion [edit]

Aquifers near the coast accept a lens of freshwater almost the surface and denser seawater under freshwater. Seawater penetrates the aquifer diffusing in from the ocean and is denser than freshwater. For porous (i.e., sandy) aquifers near the declension, the thickness of freshwater atop saltwater is about 12 metres (xl ft) for every 0.3 m (i ft) of freshwater head in a higher place sea level. This human relationship is called the Ghyben-Herzberg equation. If too much footing water is pumped almost the coast, table salt-water may intrude into freshwater aquifers causing contagion of potable freshwater supplies. Many coastal aquifers, such as the Biscayne Aquifer almost Miami and the New Jersey Coastal Obviously aquifer, have problems with saltwater intrusion as a result of overpumping and body of water level rise.

Salination [edit]

Aquifers in surface irrigated areas in semi-arid zones with reuse of the unavoidable irrigation water losses percolating down into the secret past supplemental irrigation from wells run the risk of salination.^[23]

Surface irrigation water normally contains salts in the order of 0.5 thousand/l or more and the annual irrigation requirement is in the order of x,000 m³/ha or more than then the annual import of table salt is in the order of 5,000 kg/ha or more.^[24]

Under the influence of continuous evaporation, the salt concentration of the aquifer water may increase continually and eventually crusade an environmental problem.

For salinity control in such a case, annually an corporeality of drainage water is to be discharged from the aquifer by means of a subsurface drainage system and disposed of through a prophylactic outlet. The drainage system may be horizontal (i.e. using pipes, tile drains or ditches) or vertical (drainage by wells). To estimate the drainage requirement, the use of a groundwater model with an agro-hydro-salinity component may be instrumental, e.one thousand. SahysMod.

Depth, droughts and overpumping [edit]

A 2021 report found that of ~39 million investigated^{[ how? ]} groundwater wells half-dozen-20% are at high take a chance of running dry if local groundwater levels decline by a few meters, or – equally with many areas and possibly more than than one-half of major aquifers^[25] – continue to decline.^{[26] [27]}

By country or continent [edit]

Africa [edit]

Aquifer depletion is a problem in some areas, especially in northern Africa, where one example is the Great Manmade River projection of Libya. However, new methods of groundwater management such as artificial recharge and injection of surface waters during seasonal wet periods has extended the life of many freshwater aquifers, especially in the United States.

Australia [edit]

The Great Artesian Bowl situated in Commonwealth of australia is arguably the largest groundwater aquifer in the world^[28] (over ane.7 million km^two or 0.66 million sq mi). Information technology plays a large part in water supplies for Queensland, and some remote parts of S Australia.

Canada [edit]

Discontinuous sand bodies at the base of the McMurray Germination in the Athabasca Oil Sands region of northeastern Alberta, Canada, are unremarkably referred to every bit the Basal Water Sand (BWS) aquifers.^[29] Saturated with water, they are bars beneath impermeable bitumen-saturated sands that are exploited to recover bitumen for constructed crude oil product. Where they are deep-lying and recharge occurs from underlying Devonian formations they are saline, and where they are shallow and recharged by surface water they are non-saline. The BWS typically pose issues for the recovery of bitumen, whether by open-pit mining or by in situ methods such as steam-assisted gravity drainage (SAGD), and in some areas they are targets for waste product-h2o injection.^{[xxx] [31] [32]}

South America [edit]

The Guarani Aquifer, located beneath the surface of Argentina, Brazil, Paraguay, and Uruguay, is one of the world'due south largest aquifer systems and is an of import source of fresh h2o.^[33] Named later on the Guarani people, information technology covers 1,200,000 km² (460,000 sq mi), with a volume of about forty,000 kmⁱⁱⁱ (nine,600 cu mi), a thickness of between 50 and 800 m (160 and ii,620 ft) and a maximum depth of near i,800 yard (5,900 ft).

United states [edit]

The Ogallala Aquifer of the cardinal United States is one of the world's groovy aquifers, only in places it is being quickly depleted by growing municipal use, and continuing agricultural use. This huge aquifer, which underlies portions of eight states, contains primarily fossil water from the time of the last glaciation. Annual recharge, in the more barren parts of the aquifer, is estimated to total only about 10 percent of annual withdrawals. Co-ordinate to a 2013 report by the United States Geological Survey (USGS), the depletion between 2001 and 2008, inclusive, is near 32 percentage of the cumulative depletion during the entire 20th century."^[34]

In the United States, the biggest users of h2o from aquifers include agricultural irrigation and oil and coal extraction.^[35] "Cumulative total groundwater depletion in the United States accelerated in the late 1940s and continued at an almost steady linear rate through the stop of the century. In improver to widely recognized environmental consequences, groundwater depletion also adversely impacts the long-term sustainability of groundwater supplies to aid meet the Nation's h2o needs."^[34]

An instance of a meaning and sustainable carbonate aquifer is the Edwards Aquifer^[36] in key Texas. This carbonate aquifer has historically been providing high quality h2o for nearly 2 million people, and fifty-fifty today, is full considering of tremendous recharge from a number of expanse streams, rivers and lakes. The primary risk to this resources is human development over the recharge areas.

Run across also [edit]

• Aquifer storage and recovery
• Aquifer properties
• Artesian aquifer – Confined aquifer containing groundwater nether positive pressure
• Cistern – Waterproof receptacle for holding liquids, usually water
• Hydraulic tomography
• Overexploitation – Depleting a renewable resource
• Rock (geology) – Naturally occurring mineral aggregate
• Seasonal thermal energy storage – Storage of heat or cold for periods of up to several months - aquifers may be used for storing heat between opposing seasons and for ecologically heating/cooling greenhouses, buildings, and district systems
• Leap (hydrology) – Signal at which water emerges from an aquifer to the surface
• Surficial aquifer
• Catchment hydrology

References [edit]

1. ^ "aquitard: Definition from". Answers.com. Archived from the original on 29 September 2010. Retrieved half-dozen September 2010.
2. ^ "Aquifers and Groundwater". USGS. ...more than than 30,000 feet. On boilerplate, however, the porosity and permeability of rocks decrease as their depth beneath country surface increases; the pores and cracks in rocks at great depths are closed or greatly reduced in size because of the weight of overlying rocks.
3. ^ Society, National Geographic (2019-07-thirty). "Aquifers". National Geographic Society . Retrieved 2021-09-17 .
4. ^ "Huge reserves of freshwater prevarication below the ocean floor". Gizmag.com. 11 December 2013. Retrieved fifteen December 2013.
5. ^ Post, V. E. A.; Groen, J.; Kooi, H.; Person, K.; Ge, S.; Edmunds, Due west. M. (2013). "Offshore fresh groundwater reserves every bit a global phenomenon". Nature. 504 (7478): 71–78. Bibcode:2013Natur.504...71P. doi:10.1038/nature12858. PMID 24305150. S2CID 4468578.
6. ^ "Morphological Features of Soil Wetness". Ces.ncsu.edu. Archived from the original on 9 August 2010. Retrieved half dozen September 2010.
7. ^ The energy balance of groundwater flow applied to subsurface drainage in anisotropic soils by pipes or ditches with entrance resistance. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. On line : [1] Archived 2009-02-19 at the Wayback Motorcar . Paper based on: R.J. Oosterbaan, J. Boonstra and Thou.5.G.K. Rao, 1996, "The energy balance of groundwater catamenia". Published in V.P.Singh and B.Kumar (eds.), Subsurface-Water Hydrology, pp. 153–sixty, Vol. 2 of Proceedings of the International Briefing on Hydrology and Water Resources, New Delhi, Bharat, 1993. Kluwer Academic Publishers, Dordrecht, Kingdom of the netherlands. ISBN 978-0-7923-3651-8 . On line : [2] . The corresponding "EnDrain" software can be downloaded from : [3], or from : [four]
8. ^ ILRI (2000), Subsurface drainage by (tube)wells: Well spacing equations for fully and partially penetrating wells in uniform or layered aquifers with or without anisotropy and entrance resistance, 9 pp. Principles used in the "WellDrain" model. International Constitute for Land Reclamation and Improvement (ILRI), Wageningen, Holland. On line : [5] . Download "WellDrain" software from : [6], or from : [vii]
9. ^ ^{a b c d e} Assaad, Fakhry; LaMoreaux, Philip; Hughes, Travis (2004). Field methods for geologists and hydrogeologists. Berlin, Germany: Springer-Verlag Berlin Heidelberg. doi:10.1007/978-3-662-05438-3. ISBN978-iii-540-40882-vi.
10. ^ ^{a b} Pettijohn, Francis; Potter, Paul; Siever, Raymond (1987). Sand and Sandstone. New York: Springer Science+Business organisation Media. doi:x.1007/978-one-4612-1066-5. ISBN978-0-387-96350-1.
11. ^ Alley, William; Reilly, Thomas; Franke, O. (1999). Sustainability of basis-water resources . Circular 1186. Denver, Colorado: U.S. Geological Survey. p. 8. doi:10.3133/cir1186. ISBN978-0-607-93040-5.
12. ^ Dreybrodt, Wolfgang (1988). Processes in karst systems: physics, chemistry, and geology. Springer Series in Physical Environs. Vol. four. Berlin: Springer. pp. 2–3. doi:10.1007/978-3-642-83352-6. ISBN978-3-642-83354-0.
13. ^ ^{a b} Taylor, Charles (1997). Delineation of ground-water basins and recharge areas for municipal h2o-supply springs in a karst aquifer arrangement in the Elizabethtown area, Northern Kentucky (PDF). H2o-Resources Investigations Report 96-4254. Denver, Colorado: U.Due south. Geological Survey. doi:10.3133/wri964254.
14. ^ Taylor, Charles; Greene, Earl (2008). "Hydrogeologic characterization and methods used in the investigation of karst hydrology." (PDF). Field Techniques for Estimating H2o Fluxes Betwixt Surface Water and Ground Water. Techniques and Methods 4–D2. U.S. Geological Survey. p. 107.
15. ^ Renken, R.; Cunningham, Yard.; Zygnerski, K.; Wacker, M.; Shapiro, A.; Harvey, R.; Metge, D.; Osborn, C.; Ryan, J. (November 2005). "Assessing the Vulnerability of a Municipal Well Field to Contagion in a Karst Aquifer". Environmental and Engineering science Geoscience. GeoScienceWorld. 11 (4): 320. CiteSeerXx.1.ane.372.1559. doi:x.2113/11.4.319.
16. ^ Fetter, Charles (1988). Practical Hydrology. Columbus, Ohio: Merrill. pp. 294–295. ISBN978-0-675-20887-1.
17. ^ Scanlon, Bridget; Mace, Robert; Barrett, Michael; Smith, Brian (2003). "Can we simulate regional groundwater flow in a karst system using equivalent porous media models? Instance written report, Barton Springs Edwards aquifer, USA". Journal of Hydrology. Elsevier Science. 276 (i–4): 142. Bibcode:2003JHyd..276..137S. doi:ten.1016/S0022-1694(03)00064-7.
18. ^ "International Waters". United nations Evolution Programme. Archived from the original on 27 January 2009.
19. ^ Sanchez, Rosario; Eckstein, Gabriel (2017). "Aquifers Shared Between United mexican states and the The states: Management Perspectives and Their Transboundary Nature" (PDF). Groundwater. 55 (4): 495–505. doi:10.1111/gwat.12533. PMID 28493280.
20. ^ "Transboundary Groundwater" (PDF). Water Resources Bear upon. 20 (iii). May 2018.
21. ^ "Facts About Global Groundwater Usage". National Ground Water Association . Retrieved 29 March 2021.
22. ^ Lall, Upmanu; Josset, Laureline; Russo, Tess (2020-10-17). "A Snapshot of the World's Groundwater Challenges". Almanac Review of Environment and Resources. 45 (i): 171–194. doi:x.1146/annurev-environ-102017-025800. ISSN 1543-5938.
23. ^ ILRI (1989), Effectiveness and Social/Environmental Impacts of Irrigation Projects: a Review (PDF), In: Annual Study 1988 of the International Establish for Land Reclamation and Comeback (ILRI), Wageningen, The Netherlands, pp. 18–34
24. ^ ILRI (2003), Drainage for Agriculture: Drainage and hydrology/salinity - water and common salt balances. Lecture notes International Course on Land Drainage, International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. Download from : [8], or directly as PDF : [nine]
25. ^ Famiglietti, James South.; Ferguson, Grant (23 April 2021). "The subconscious crisis beneath our feet". Science. pp. 344–345. doi:ten.1126/science.abh2867. Retrieved ten May 2021.
26. ^ "The largest cess of global groundwater wells finds many are at take chances of drying up". ScienceDaily . Retrieved 10 May 2021.
27. ^ Jasechko, Scott; Perrone, Debra (23 Apr 2021). "Global groundwater wells at risk of running dry". Science. 372 (6540): 418–421. doi:10.1126/science.abc2755. ISSN 0036-8075. Retrieved 10 May 2021.
28. ^ "The Great Artesian Bowl" (PDF). Facts: Water Serial. Queensland Department of Natural Resources and Water. Archived from the original (PDF) on xiii November 2006. Retrieved 3 January 2007.
29. ^ Joslyn N Mine Project: Environmental Bear on Cess Hydrologeology (PDF) (Report). Edmonton, Alberta: Deer Creek Free energy. December 2005. p. 4. Archived from the original (PDF) on 2 December 2013.
30. ^ Barson, D., Bachu, S. and Esslinger, P. 2001. Period systems in the Mannville Group in the east-central Athabasca surface area and implications for steam-assisted gravity drainage (SAGD) operations for in situ bitumen production. Bulletin of Canadian Petroleum Geology, vol. 49, no. 3, pp. 376–92.
31. ^ Griffiths, Mary; Woynillowicz, Dan (April 2003). Oil and Troubled Waters: Reducing the impact of the oil and gas industry on Alberta's h2o resources (PDF) (Written report). Edmonton, Alberta: Pembina Institute.
32. ^ FMFN (June 2012). Fort McKay's Review of Teck Resource Ltd. – Frontier Oil Sands Mine Project Integrated Awarding (PDF) (Report). Fort McKay Get-go Nation.
33. ^ Brittain, John (22 June 2015). "The International Atomic Free energy Agency: Linking Nuclear Scientific discipline and Affairs". Science and Affairs.
34. ^ ^{a b} Konikow, Leonard F. Groundwater Depletion in the United States (1900–2008) (PDF) (Report). Scientific Investigations Report. Reston, VA: U.S. Department of the Interior, U.S. Geological Survey. p. 63.
35. ^ Zabarenko, Deborah (xx May 2013). "Drop in U.Due south. undercover water levels has accelerated: USGS". Reuters. Washington, DC.
36. ^ "Edwards Aquifer Authority". Edwardsaquifer.org. Retrieved 15 December 2013.

External links [edit]

• IGRAC International Groundwater Resources Assessment Centre
• The Groundwater Projection - Online platform for groundwater knowledge

johnsontheyeaterve.blogspot.com

Source: https://en.wikipedia.org/wiki/Aquifer

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