An aquifer is an underground layer of water Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state, water vapor or steam-bearing permeable rock or unconsolidated materials (gravel Gravel is rock that is of a specific particle size range. Specifically, it is any loose rock that is larger than 2 mm in its smallest dimension (about 1/12 of an inch) and no more than 64 mm (2.5 in). The next smaller size class in geology is sand, which is >0.0625 to 2 mm (0.0025 to 0.0787 in) in size. The next larger size is cobble, which is &, sand Sand is a naturally occurring granular material composed of finely divided rock and mineral particles, silt Silt is granular material of a grain size between sand and clay derived from soil or rock. Silt may occur as a soil or as suspended sediment in a surface water body. It may also exist as soil deposited at the bottom of a water body, or clay Clay is a naturally occurring material composed primarily of fine-grained minerals. Clay deposits are mostly composed of clay minerals, a subtype of phyllosilicate minerals, which impart plasticity and harden when fired or dried; they also may contain variable amounts of water trapped in the mineral structure by polar attraction. Organic materials) from which groundwater Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called can be usefully extracted using a water well A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a vertical turbine pump, a handpump or a mechanical pump . It can also be drawn up using containers, such as buckets, that are raised. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust, (commonly in aquifers). The term geohydrology is often used interchangeably. Some make the minor distinction between a hydrologist or engineer applying themselves to geology (geohydrology), and a geologist. Related terms include aquitard, which is a bed of low permeability along an aquifer[1], and aquiclude (or aquifuge), which is a solid, impermeable area underlying or overlying an aquifer. The surface of saturated material in an aquifer is known as the water table The water table is the level at which the groundwater pressure is equal to atmospheric pressure. It may be conveniently visualized as the 'surface' of the groundwater in a given vicinity. It usually coincides approximately with the 'phreatic surface', but can be many feet above it. As water infiltrates through pore spaces in the soil, it first.
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Aquifer depth
Aquifers can occur at various depths. Those closer to the surface are not only more likely to be used for water supply and irrigation, but are also more likely to be topped up by the local rainfall. Many desert areas have limestone hills or mountains within them or close to them that can be exploited as groundwater resources. Parts of the Atlas Mountains The Atlas Mountains are a mountain range across a northern stretch of Africa extending about 2,500 km (1,500 miles) through Morocco, Algeria, and Tunisia. The highest peak is the Toubkal mountain, with an elevation of 4,167 metres (13,671 ft) in southwestern Morocco. The Atlas ranges separate the Mediterranean and Atlantic coastlines from the in North Africa North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes seven countries or territories; Algeria, Egypt, Libya, Morocco, Sudan, Tunisia, and Western Sahara Algeria, Morocco, Tunisia, Mauritania, and, the Lebanon Mount Lebanon , as a geographic designation, is the Lebanese mountain range, known as the Western Mountain Range of Lebanon. It extends across the whole country along about 160 km (99 mi), parallel to the Mediterranean coast with the highest peak, Qurnat as Sawda', at 3,088 m (10,130 ft). Lebanon has historically been defined by these mountains, and Anti-Lebanon ranges of Syria Syria , officially the Syrian Arab Republic (Arabic: الجمهورية العربية السورية), is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest, Israel Israel , officially the State of Israel (Hebrew: מְדִינַת יִשְׂרָאֵל (help·info), Medīnat Yisrā'el; Arabic: دَوْلَةُ إِسْرَائِيلَ, Dawlat Isrā'īl), is a country in Western Asia located on the eastern shore of the Mediterranean Sea. It borders Lebanon in the north, Syria in the northeast, Jordan and the and Lebanon, the Jebel Akhdar (Oman) in Oman Oman , officially the Sultanate of Oman (Arabic: سلطنة عمان Salṭanat ʻUmān), is an Arab country in southwest Asia on the southeast coast of the Arabian Peninsula. It borders the United Arab Emirates on the northwest, Saudi Arabia on the west and Yemen on the southwest, parts of the Sierra Nevada The Sierra Nevada is a mountain range located in California and Nevada, United States. The range is also known informally as "the Sierra," "the High Sierra," and "the Sierras." and neighbouring ranges in the United States' Southwest The Southwestern United States is a region defined in different ways by different sources. Broad definitions include nearly a quarter of the United States, including California, Nevada, Arizona, New Mexico, Utah, Colorado, Oklahoma, and Texas. Narrowly defined, the "core" Southwest might include only Arizona and New Mexico, with parts of, have shallow aquifers that are exploited for their water. Over-exploitation Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. If sustained, it can lead to the destruction of the resource. The term can be applied to various natural resources such as wild medicinal plants, grazing pastures, fish stocks, forests and water aquifers 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 as Libya Libya (Arabic: ليبيا Lībiyā pronunciation ; Libyan vernacular: Lībya pronunciation (help·info); Amazigh: ), officially the Great Socialist People's Libyan Arab Jamahiriya ( Arabic: الجماهيرية العربية الليبية الشعبية الإشتراكية العظمى Al-Jamāhīriyyah al-ʿArabiyyah al-Lībiyyah aš-Š and Israel Israel , officially the State of Israel (Hebrew: מְדִינַת יִשְׂרָאֵל (help·info), Medīnat Yisrā'el; Arabic: دَوْلَةُ إِسْرَائِيلَ, Dawlat Isrā'īl), is a country in Western Asia located on the eastern shore of the Mediterranean Sea. It borders Lebanon in the north, Syria in the northeast, Jordan and the, population growth has led to over-population, which has caused the lowering of water table and the subsequent contamination of the groundwater Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called with saltwater from the sea A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, the term refers to a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean. It is also used sometimes to describe a large saline lake that lacks a natural outlet, such as the Caspian Sea (saline intrusions).
The beach A beach is a geological landform along the shoreline of an ocean, sea or lake. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles, waves or cobblestones. The particles of which the beach is composed can sometimes instead have biological origins, such as shell fragments or coralline algae provides a model to help visualize an aquifer. If a hole is dug into the sand Sand is a naturally occurring granular material composed of finely divided rock and mineral particles, very wet or saturated sand will be located at a shallow depth. This hole is a crude well A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a vertical turbine pump, a handpump or a mechanical pump . It can also be drawn up using containers, such as buckets, that are raised, the wet sand represents an aquifer, and the level to which the water rises in this hole represents the water table The water table is the level at which the groundwater pressure is equal to atmospheric pressure. It may be conveniently visualized as the 'surface' of the groundwater in a given vicinity. It usually coincides approximately with the 'phreatic surface', but can be many feet above it. As water infiltrates through pore spaces in the soil, it first.
Classification
Typical aquifer cross-sectionThis diagram indicates typical flow directions in a cross-sectional In geometry, a cross-section is the intersection of a figure in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc. More plainly, when cutting an object into slices one gets many parallel cross-sections view of a simple confined/unconfined aquifer system. The system 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 A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, crick, kill, lick, rill, river syke, bayou, rivulet, streamage, wash, run or runnel. In some countries or communities a stream may be defined by (typical in humid Humidity is the amount of water vapor in the air. Relative humidity is defined as the ratio of the partial pressure of water vapor in a parcel of air to the saturated vapor pressure of water vapor at a prescribed temperature. Humidity may also be expressed as specific humidity. Relative humidity is an important metric used in forecasting weather regions). The water table The water table is the level at which the groundwater pressure is equal to atmospheric pressure. It may be conveniently visualized as the 'surface' of the groundwater in a given vicinity. It usually coincides approximately with the 'phreatic surface', but can be many feet above it. As water infiltrates through pore spaces in the soil, it first and unsaturated zone The vadose zone, also termed the unsaturated zone, is the portion of Earth between the land surface and the phreatic zone or zone of saturation . It extends from the top of the ground surface to the water table. Water in the vadose zone has a pressure head less than atmospheric pressure, and is retained by a combination of adhesion (funiculary are also illustrated.
An aquitard is a zone within the earth that restricts the flow of groundwater Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called from one aquifer to another. An aquitard can sometimes, if completely impermeable, be called an aquiclude or aquifuge. Aquitards are composed of layers of either clay Clay is a naturally occurring material composed primarily of fine-grained minerals. Clay deposits are mostly composed of clay minerals, a subtype of phyllosilicate minerals, which impart plasticity and harden when fired or dried; they also may contain variable amounts of water trapped in the mineral structure by polar attraction. Organic materials or non-porous rock In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids with low hydraulic conductivity Hydraulic conductivity, symbolically represented as K, is a property of vascular plants, soil or rock, that describes the ease with which water can move through pore spaces or fractures. It depends on the intrinsic permeability of the material and on the degree of saturation. Saturated hydraulic conductivity, Ksat, describes water movement through.
Saturated versus unsaturated
Groundwater Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called can be found at nearly every point in the Earth's shallow subsurface, to some degree; although aquifers do not necessarily contain fresh water Freshwater or fresh water is naturally occurring water on the Earth's surface in bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Freshwater is characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and. The Earth's crust can be divided into two regions: the saturated Water content or moisture content is the quantity of water contained in a material, such as soil , rock, ceramics, or wood on a volumetric or gravimetric basis. The property is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 (completely dry) to the value of the materials' porosity at zone or phreatic The term phreatic is used in Earth sciences to refer to matters relating to ground water below the static water table . The term 'phreatic surface' is where the hydrostatic pressure of groundwater or soil moisture is atmospheric (or pressure head is zero). This surface normally coincides with the water table zone (e.g., aquifers, aquitards, etc.), where all available spaces are filled with water, and the unsaturated zone (also called the vadose zone The vadose zone, also termed the unsaturated zone, is the portion of Earth between the land surface and the phreatic zone or zone of saturation . It extends from the top of the ground surface to the water table. Water in the vadose zone has a pressure head less than atmospheric pressure, and is retained by a combination of adhesion (funiculary), where there are still pockets of air with some water, but can be filled with more water.
Saturated means the pressure head of the water is greater than atmospheric pressure Atmospheric pressure is the force per unit area exerted against a surface by the weight of air above that surface in the Earth's atmosphere. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. Low pressure areas have less atmospheric mass above (it has a gauge pressure > 0). The definition of the water table The water table is the level at which the groundwater pressure is equal to atmospheric pressure. It may be conveniently visualized as the 'surface' of the groundwater in a given vicinity. It usually coincides approximately with the 'phreatic surface', but can be many feet above it. As water infiltrates through pore spaces in the soil, it first is surface where the pressure head Hydraulic head or piezometric head is a specific measurement of water pressure above a geodetic datum. It is usually measured as a water surface elevation, expressed in units of length, at the entrance of a piezometer. In an aquifer, it can be calculated from the depth to water in a piezometric well (a specialized water well), and given is equal to atmospheric pressure (where gauge pressure =0).
Unsaturated conditions occur above the water table where the pressure head is negative (absolute pressure can never be negative, but gauge pressure can) and the water that incompletely fills the pores of the aquifer material is under suction Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not innately attract matter. Dust being "sucked". The water content Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust, (commonly in aquifers). The term geohydrology is often used interchangeably. Some make the minor distinction between a hydrologist or engineer applying themselves to geology (geohydrology), and a geologist Unsaturated means the zone is held in place by surface adhesive forces Adhesion is any attraction process between dissimilar molecular species that can potentially bring them in "direct contact".[clarification needed] By contrast cohesion takes place between similar molecules and it rises above the water table (the zero gauge pressure Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust, (commonly in aquifers). The term geohydrology is often used interchangeably. Some make the minor distinction between a hydrologist or engineer applying themselves to geology (geohydrology), and a geologist isobar) by capillary action Capillary action, or capillarity, refers to certain phenomena associated with the behavior of liquids in thin tubes or in porous materials. Liquids, such as water, will tend to move "up-hill" which does not normally occur in large containers. The interface between liquids, or a liquid and a gas, can form a meniscus or crescent shape to saturate a small zone above the phreatic surface (the capillary fringe) at less than atmospheric pressure. This is termed tension saturation and is not the same as saturation on a water content basis. Water content in a capillary fringe decreases with increasing distance from the phreatic surface. The capillary head depends on soil pore size. In sandy Sand is a naturally occurring granular material composed of finely divided rock and mineral particles soils with larger pores, the head will be less than in clay Clay is a naturally occurring material composed primarily of fine-grained minerals. Clay deposits are mostly composed of clay minerals, a subtype of phyllosilicate minerals, which impart plasticity and harden when fired or dried; they also may contain variable amounts of water trapped in the mineral structure by polar attraction. Organic materials soils with very small pores. The normal capillary rise in a clayey soil is less than 1.80 m (six feet) but can range between 0.3 and 10 m (1 and 30 ft). [6]
The capillary rise of water in a small diameter tube is this same physical process. The water table is the level to which water will rise in a large-diameter pipe (e.g., a well) that goes down into the aquifer and is open to the atmosphere.
See also: Water content and Soil moistureAquifers versus aquitards
Aquifers are typically saturated regions of the subsurface that 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).
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 comprise layers of either clay or non-porous rock with low hydraulic conductivity.
In mountainous areas (or near rivers in mountainous areas), the main 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 two-dimensional slice of the aquifer) appear to be layers of alternating coarse and fine materials. Coarse materials, because of the high energy needed to move them, tend to be found nearer the source (mountain fronts or rivers), whereas the fine-grained material will make it farther from the source (to the flatter parts of the basin or overbank areas - sometimes called the pressure area). Since there are less fine-grained deposits near the source, this is a place where aquifers are often unconfined (sometimes called the forebay area), or in hydraulic communication with the land surface.
See also: Hydraulic conductivity and StorativityConfined versus unconfined
There are two end members in the spectrum of types of aquifers; confined and unconfined (with semi-confined being in between). Unconfined aquifers are sometimes also called water table or phreatic aquifers, because their upper boundary is the water table or phreatic surface. (See Biscayne Aquifer.) Typically (but not always) the shallowest aquifer at a given location is unconfined, meaning it does not have a confining layer (an aquitard or aquiclude) between it and the surface. The term "perched" refers to ground water accumulating above 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 water that occurs at an elevation higher than a regionally-extensive aquifer. The difference between perched and unconfined aquifers is their size (perched is smaller).
If the distinction between confined and unconfined is not clear geologically (i.e., if it is not known if a clear confining layer exists, or if the geology is more complex, e.g., a fractured bedrock aquifer), the value of storativity returned from an aquifer test can be 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 little as 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 have storativities (typically then called specific yield) greater than 0.01 (1% of bulk volume); they release water from storage by the mechanism of actually draining the pores of the aquifer, releasing relatively large amounts of water (up to the drainable porosity of the aquifer material, or the minimum volumetric water content).
See also: Porosity and StorativityIsotropic versus anisotropic
In isotropic aquifers or aquifer layers the hydraulic conductivity (K) 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 system, even when the separate layers are isotropic, because the compound Kh and Kv values are different (see hydraulic conductivity#Transmissivity and hydraulic conductivity#Resistance). When calculating flow to drains [2] or to wells [3] in an aquifer, the anisotropy is to be taken into account lest the resulting design of the drainage system may be faulty.
Groundwater in rock formations
Groundwater may exist in underground rivers (e.g., caves where water flows freely underground). This may occur in eroded limestone areas known as karst topography, which make up only a small percentage of Earth's area. More usual is that the pore spaces of rocks in the subsurface are simply saturated with water — like a kitchen sponge — which can be pumped out for agricultural, industrial, or municipal uses.
If a rock unit of low porosity is highly fractured, it can also make a good aquifer (via fissure flow), provided the rock has an appreciable hydraulic conductivity to facilitate movement of water. Porosity is important, but, alone, it does not determine a rock's ability of being an aquifer. Areas of the Deccan Traps (a basaltic lava) in west central India are good examples of rock formations with high porosity but low permeability, which makes them poor aquifers. Similarly, the micro-porous (Upper Cretaceous) Chalk of south east England, although having a reasonably high porosity, has a low grain-to-grain permeability, with much of its good water-yielding characteristics being due to micro-fracturing and fissuring.
Human dependence on groundwater
Center-pivot irrigated fields in Kansas covering hundreds of square miles watered by the Ogallala AquiferMost land areas on Earth have some form of aquifer underlying them, sometimes at significant depths.
Fresh-water aquifers, especially those with limited recharge by meteoric water, can be over-exploited and, depending on the local hydrogeology, may draw in non-potable water or saltwater (saltwater intrusion) from hydraulically connected aquifers or surface water bodies. This can be a serious problem, especially in coastal areas and other areas where aquifer pumping is excessive. In some areas, the ground water can be contaminated by mineral poisons, such as arsenic - see Arsenic contamination of groundwater.
Aquifers are critically important in human habitation and agriculture. Deep aquifers in arid areas have long been water sources for irrigation (see Ogallala below). Many villages and even large cities draw their water supply from wells in aquifers.
Municipal, irrigation, and industrial water supplies are provided through large wells. Multiple wells for one water supply source are termed "wellfields", which may withdraw water from confined or unconfined aquifers. Using ground water from deep, confined aquifers provides more protection from surface water contamination. Some wells, termed "collector wells," are specifically designed to induce infiltration of surface (usually river) water.
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. This recharge is typically from rivers or meteoric water (precipitation) that percolates into the aquifer through overlying unsaturated materials.
Subsidence
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 water pressure in the sand and gravel causes slow drainage of water from the adjoining confining layers. If these confining layers are composed of compressible silt or clay, the loss of water to the aquifer reduces the water 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 as 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 hold water.
Saltwater intrusion
Main article: Saltwater intrusionAquifers near the coast have a lens of freshwater near 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 coast, the thickness of freshwater atop saltwater is about 40 feet (12 m) for every 1 ft (0.30 m) of freshwater head above sea level. This relationship is called the Ghyben-Herzberg equation. If too much ground water is pumped near the coast, salt-water may intrude into freshwater aquifers causing contamination of potable freshwater supplies. Many coastal aquifers, such as the Biscayne Aquifer near Miami and the New Jersey Coastal Plain aquifer, have problems with saltwater intrusion as a result of overpumping.
Salination
Example of a water balance of the aquiferAquifers in surface irrigated areas in (semi)arid zones with reuse of the unavoidable irrigation water losses percolating down into the underground by supplemental irrigation from wells run the risk of salination. Surface irrigation water normally contains salts in the order of 0.5 g/l or more and the annual irrigation requirement is in the order of 10000 m3/ha or more so that the annual import of salt is in the order of 5000 kg/ha or more [4] . Under the influence of continuous evaporation, the salt concentration of the aquifer water may increase continually and eventually cause an environmental problem.
For salinity control in such a case, annually an amount of drainage water is to be discharged from the aquifer and disposed of through a safe outlet. To estimate the drainage requirement, the use of a groundwater model with an agro-hydro-salinity component may be instrumental, e.g., SahysMod.
Examples of aquifers
An example of a significant and sustainable carbonate aquifer is the Edwards Aquifer [7] in central Texas. This carbonate aquifer has historically been providing high quality water for nearly 2 million people, and even today, is completely full because of tremendous recharge from a number of area streams, rivers and lakes. The primary risk to this resource is human development over the recharge areas.
The Great Artesian Basin situated in Australia is arguably the largest groundwater aquifer in the world [5] (over 1.7 million km²). It plays a large part in water supplies for Queensland and remote parts of South Australia.
The Guarani Aquifer with an area of 1.2 million km² is shared by Brazil, Argentina, Paraguay and Uruguay.
Aquifer depletion is a problem in some areas, and is especially critical in northern Africa; see the Great Manmade River project of Libya for an example. 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.
North America
Withdrawal rates from the Ogallala Aquifer Wetlands contrast the arid landscape around Middle Spring, Fish Springs National Wildlife Refuge, Utah.- Oak Ridges Moraine, north of the city of Toronto.
- The Ogallala Aquifer of the central United States is one of the world's great aquifers, but in places it is being rapidly 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 arid parts of the aquifer, is estimated to total only about 10 percent of annual withdrawals.
- The Edwards Aquifer in Texas is important as a water supply aquifer and the source of major springs.
- Known by many names, The Basin and Range Carbonate Aquifer is an important and unique aquifer in that it covers several western states and basins. Groundwater flows through fractured carbonate rock beneath basins and leads to many regional springs and water features, like Fish Springs National Wildlife Refuge and the springs at Death Valley. This has been studied in extensive projects like the USGS BARCASS report[6] and is controversial due to water issues like that in Snake Valley, Utah.
- The Kirkwood-Cohansey Aquifer, located under the Pine Barrens (New Jersey) of southern New Jersey, contains 17 trillion US gallons (64 km³) of some of the purest water in the United States.
- The Mahomet Aquifer supplies water to some 800,000 people in central Illinois and contains approximately four trillion US gallons (15 km³) of water. The Mahomet Aquifer Consortium [8] was formed in 1998 to study the aquifer with hopes of ensuring the water supply and reducing potential user conflicts.
- The Spokane Valley - Rathdrum Prairie Aquifer covers 325 square miles (842 km2) in eastern Washington and Idaho. It provides drinking water for some 400,000 people.
- The state of Washington has numerous large aquifers, as shown in this map of the Hydrogeology of Washington State.
- The San Diego Formation is a water aquifer for San Diego, California [7] and Los Angeles, California.
See also
- Aquifer Storage and Recovery
- Artesian aquifer
- Cistern
- Groundwater model
- List of aquifers
- Overexploitation
- Seasonal thermal store; aquifers may be used as heat/cold stores for ecologically heating/cooling homes and greenhouses
External links
- Map of United States Aquifers
- Florida's Springs and Aquifer
- Falling Water Tables
- Bibliography on Water Resources and International Law Peace Palace Library
- IGRAC International Groundwater Resources Assessment Centre
- [9] Free download of SahysMod aquifer model. Manual on line: [10] (PDF)
References
- ^ http://www.answers.com/topic/aquitard
- ^ R.J.Oosterbaan, 1997, The energy balance of groundwater flow applied to subsurface drainage in anisotropic soils by pipes or ditches with entrance resistance. On line: [1] (PDF). The corresponding free EnDrain program can be downloaded from: [2] .
- ^ R.J.Oosterbaan, 2002, Subsurface drainage by (tube)wells, 9 pp. On line: [3] (PDF). The correspondig free WellDrain program can be downloaded from: [4] .
- ^ R.J.Oosterbaan, 2000, Drainage and hydrology/salinity: water and salt balances. On line: [5] (PDF)
- ^ "The Great Artesian Basin" (PDF). Facts: Water Series. Queensland Department of Natural Resources and Water. http://www.nrw.qld.gov.au/factsheets/pdf/water/w68.pdf. Retrieved 2007-01-03.
- ^ http://nevada.usgs.gov/barcass/index.htm
- ^ San Diego County Water Authority - Water Management - Local Resources
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Categories: Aquifers | Hydraulic engineering | Hydrology | Hydrogeology | Water and the environment
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