Difference between revisions of "Groundwater" - New World Encyclopedia

From New World Encyclopedia
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The following are some definitions of groundwater.
 
The following are some definitions of groundwater.
  
United States Geological Survey
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'''United States Geological Survey''' (Langbein and Iseri 1960)
{quote}
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* Ground water. Water in the ground that is in the zone of saturation, from which wells, springs, and ground-water runoff are supplied."  
+
[http://water.usgs.gov/wsc/glossary.html Science in Your Watershed: General Introduction and Hydrologic Definitions
* Zone of aeration. The zone above the water table. Water in the zone of aeration does not flow into a well.
+
W. B. LANGBEIN and KATHLEEN T.ISERI
* Zone of saturation. The zone in which the functional permeable rocks are saturated with water under hydrostatic pressure. (Meinzer, 1923, p. 21.) Water in the zone of saturation will flow into a well, and is called ground water.  
+
 
{/quote}
+
Manual of Hydrology: Part 1. General Surface-Water Techniques
 +
GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1541-A
 +
Methods and practices of the Geological Survey
 +
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1960
 +
 
 +
 
 +
* "Ground water. Water in the ground that is in the zone of saturation, from which wells, springs, and ground-water runoff are supplied."  
 +
* "Zone of aeration. The zone above the water table. Water in the zone of aeration does not flow into a well."
 +
* "Zone of saturation. The zone in which the functional permeable rocks are saturated with water under hydrostatic pressure.. . Water in the zone of saturation will flow into a well, and is called ground water."
 +
 
 +
 
 +
'''New York State Department of Environmental Conservation''' (2013).
 +
 
 +
* New York State Department of Environmental Conservation (DEC). 2013. [http://www.dec.ny.gov/lands/76322.html Groundwater definitions]. ''NY State Dept. of Environmental Conservation''. Retrieved January 2, 2013.
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 +
 
 +
Groundwater: Water found in the spaces between soil particles and cracks in rocks underground located in the saturation zone. Cracks in rocks can be due to joints, faults, etc. Groundwater is a natural resource that is used for drinking, recreation, industry, and growing crops.
 +
 
 +
Saturated zone: Located immediately below the unsaturated zone (see definition below) where the pores are totally saturated with water. Same as "groundwater".
 +
Unsaturated zone: Located immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. Plant roots can capture the moisture passing through this zone, but it cannot provide water for wells. Also known as the unsaturated zone or vadose zone.
 +
 
 +
 
 +
Pennsylvania Groundwater Policy Education Project (PA-GPEP).  (Stevens n.d.)
 +
 
 +
Stevens, E. n.d. Groundwater. A Primer for Pennsylvanians. Pennsylvania Groundwater Policy Education Project (PA-GPEP). Printed by League of Women Voters of Pennsylvania Citizen Education Found and Penn State Cooperative Extension.
 +
 
  
 
Typically, groundwater is thought of as liquid water flowing through shallow aquifers, but, in the technical sense, it can also include [[soil moisture]], [[permafrost]] (frozen soil), immobile water in very low permeability [[bedrock]], and deep [[Geothermal (geology)|geothermal]] or [[Petroleum geology|oil formation]] water. Groundwater is hypothesized to provide [[lubrication]] that can possibly influence the movement of [[Fault (geology)|fault]]s. It is likely that much of the [[Earth]]'s subsurface contains some water, which may be mixed with other fluids in some instances. Groundwater may not be confined only to the Earth. The formation of some of the [[Hydrology of Mars|landforms]] observed on [[Mars]] may have been influenced by groundwater. There is also evidence that liquid water may also exist in the subsurface of [[Jupiter]]'s moon [[Europa (moon)|Europa]].<ref>{{cite book | author=Richard Greenburg | title=The Ocean Moon: Search for an Alien Biosphere | publisher=Springer Praxis Books | year=2005}}</ref>
 
Typically, groundwater is thought of as liquid water flowing through shallow aquifers, but, in the technical sense, it can also include [[soil moisture]], [[permafrost]] (frozen soil), immobile water in very low permeability [[bedrock]], and deep [[Geothermal (geology)|geothermal]] or [[Petroleum geology|oil formation]] water. Groundwater is hypothesized to provide [[lubrication]] that can possibly influence the movement of [[Fault (geology)|fault]]s. It is likely that much of the [[Earth]]'s subsurface contains some water, which may be mixed with other fluids in some instances. Groundwater may not be confined only to the Earth. The formation of some of the [[Hydrology of Mars|landforms]] observed on [[Mars]] may have been influenced by groundwater. There is also evidence that liquid water may also exist in the subsurface of [[Jupiter]]'s moon [[Europa (moon)|Europa]].<ref>{{cite book | author=Richard Greenburg | title=The Ocean Moon: Search for an Alien Biosphere | publisher=Springer Praxis Books | year=2005}}</ref>
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Artesian (or confined) aquifer: exist where the groundwater is bounded between layers of impermeable substances like clay or dense rock. When tapped by a well, water in confined aquifers is forced up, sometimes above the land surface.
 
Artesian (or confined) aquifer: exist where the groundwater is bounded between layers of impermeable substances like clay or dense rock. When tapped by a well, water in confined aquifers is forced up, sometimes above the land surface.
 
  
 
== Aquifers ==
 
== Aquifers ==

Revision as of 04:06, 3 January 2014

Groundwater is located within the zone of saturation

Groundwater or ground water is water located within the ground's zone of saturation, where the soil pore spaces and fractures in the rock are completely filled with water. It differs from soil water, which is the water that is in the unsaturated zone, or zone of aeration, where the soil pore spaces contain air and water but are not completely saturated. The term groundwater also has been used more broadly as any water beneath the earth's surface in soil; however, the above definition is aligned with those provided by such sources as the U.S. Geological Survey, New York State Dept. of Environmental Conservation, and Pennsylvania Groundwater Policy Education Project.

The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table; in other words, below the level of the water table the soil pores and rock fractures are saturated with water. An aquifer is a layer within the zone of saturation that can readily yield and store water, such as in interconnected spaces (fractures, cracks, poor spaces, etc.) that can provide a source of water for a well.

As part of the [Biogeochemical cycle#Water cycle|hydrologic cycle]], groundwater stores and transmits water that has filtered down from the surface and it also slowly flows back to the surface, with natural discharge at places such as springs, seeps, and wetlands. Groundwater discharging into a stream provides water to allow the stream to flow throughout the year.

Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.


Definitions

Dzherelo, a common source of drinking water in a Ukrainian village.

The term groundwater has been broadly applied to any water beneath the earth's surface in soil, and thus including such features as soil moisture and permafrost (frozen soil) within areas not completely saturated with water (unsaturated zone). However, the term has been applied more technically and specifically to water below the water table, where the soil pore spaces and fractures in the rock are completely saturated with water (zone of saturation).

The following are some definitions of groundwater.

United States Geological Survey (Langbein and Iseri 1960)

[http://water.usgs.gov/wsc/glossary.html Science in Your Watershed: General Introduction and Hydrologic Definitions W. B. LANGBEIN and KATHLEEN T.ISERI

Manual of Hydrology: Part 1. General Surface-Water Techniques GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1541-A Methods and practices of the Geological Survey UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1960


  • "Ground water. Water in the ground that is in the zone of saturation, from which wells, springs, and ground-water runoff are supplied."
  • "Zone of aeration. The zone above the water table. Water in the zone of aeration does not flow into a well."
  • "Zone of saturation. The zone in which the functional permeable rocks are saturated with water under hydrostatic pressure.. . Water in the zone of saturation will flow into a well, and is called ground water."


New York State Department of Environmental Conservation (2013).

  • New York State Department of Environmental Conservation (DEC). 2013. Groundwater definitions. NY State Dept. of Environmental Conservation. Retrieved January 2, 2013.


Groundwater: Water found in the spaces between soil particles and cracks in rocks underground located in the saturation zone. Cracks in rocks can be due to joints, faults, etc. Groundwater is a natural resource that is used for drinking, recreation, industry, and growing crops.

Saturated zone: Located immediately below the unsaturated zone (see definition below) where the pores are totally saturated with water. Same as "groundwater". Unsaturated zone: Located immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. Plant roots can capture the moisture passing through this zone, but it cannot provide water for wells. Also known as the unsaturated zone or vadose zone.


Pennsylvania Groundwater Policy Education Project (PA-GPEP). (Stevens n.d.)

Stevens, E. n.d. Groundwater. A Primer for Pennsylvanians. Pennsylvania Groundwater Policy Education Project (PA-GPEP). Printed by League of Women Voters of Pennsylvania Citizen Education Found and Penn State Cooperative Extension.


Typically, groundwater is thought of as liquid water flowing through shallow aquifers, but, in the technical sense, it can also include soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water. Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of the Earth's subsurface contains some water, which may be mixed with other fluids in some instances. Groundwater may not be confined only to the Earth. The formation of some of the landforms observed on Mars may have been influenced by groundwater. There is also evidence that liquid water may also exist in the subsurface of Jupiter's moon Europa.[1]

File:AlapahaRiver2002.jpg
The entire surface water flow of the Alapaha River near Jennings, Florida going into a sinkhole leading to the Floridan Aquifer groundwater



An underground geological formation able to store and yield water (see artesian, confined, and unconfined aquifers) Unconfined aquifers: An aquifer in which the water table is at or near atmosphere pressure and is the upper boundary of the aquifer. Because the aquifer is not under pressure the water level in a well is the same as the water table outside the well.

Artesian (or confined) aquifer: exist where the groundwater is bounded between layers of impermeable substances like clay or dense rock. When tapped by a well, water in confined aquifers is forced up, sometimes above the land surface.

Aquifers

Groundwater withdrawal rates from the Ogallala Aquifer in the central U.S.
Main article: Aquifer

An aquifer is a layer of porous substrate that contains and transmits groundwater. When water can flow directly between the surface and the saturated zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are usually more saturated since gravity causes water to flow downward.

The upper level of this saturated layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone.

Substrate with low porosity that permits limited transmission of groundwater is known as an aquitard. An aquiclude is a substrate with porosity that is so low it is virtually impermeable to groundwater.

A confined aquifer is an aquifer that is overlain by a relatively impermeable layer of rock or substrate such as an aquiclude or aquitard. If a confined aquifer follows a downward grade from its recharge zone, groundwater can become pressurized as it flows. This can create artesian wells that flow freely without the need of a pump and rise to a higher elevation than the static water table at the above, unconfined, aquifer.

The characteristics of aquifers vary with the geology and structure of the substrate and topography in which they occur. In general, the more productive aquifers occur in sedimentary geologic formations. By comparison, weathered and fractured crystalline rocks yield smaller quantities of groundwater in many environments. Unconsolidated to poorly cemented alluvial materials that have accumulated as valley-filling sediments in major river valleys and geologically subsiding structural basins are included among the most productive sources of groundwater.

The high specific heat capacity of water and the insulating effect of soil and rock can mitigate the effects of climate and maintain groundwater at a relatively steady temperature. In some places where groundwater temperatures are maintained by this effect at about 10°C (50°F), groundwater can be used for controlling the temperature inside structures at the surface. For example, during hot weather relatively cool groundwater can be pumped through radiators in a home and then returned to the ground in another well. During cold seasons, because it is relatively warm, the water can be used in the same way as a source of heat for heat pumps that is much more efficient than using air.

Water cycle

Main article: Water cycle
Relative groundwater travel times.

Groundwater makes up about twenty percent of the world's fresh water supply, which is about 0.61% of the entire world's water, including oceans and permanent ice. Global groundwater storage is roughly equal to the total amount of freshwater stored in the snow and ice pack, including the north and south poles. This makes it an important resource that can act as a natural storage that can buffer against shortages of surface water, as in during times of drought.[2]

Groundwater is naturally replenished by surface water from precipitation, streams, and rivers when this recharge reaches the water table.[citation needed]

Groundwater can be a long-term 'reservoir' of the natural water cycle (with residence times from days to millennia), as opposed to short-term water reservoirs like the atmosphere and fresh surface water (which have residence times from minutes to years). The figure[3] shows how deep groundwater (which is quite distant from the surface recharge) can take a very long time to complete its natural cycle.

The Great Artesian Basin in central and eastern Australia is one of the largest confined aquifer systems in the world, extending for almost 2 million km2. By analysing the trace elements in water sourced from deep underground, hydrogeologists have been able to determine that water extracted from these aquifers can be more than 1 million years old.

By comparing the age of groundwater obtained from different parts of the Great Artesian Basin, hydrogeologists have found it increases in age across the basin. Where water recharges the aquifers along the Eastern Divide, ages are young. As groundwater flows westward across the continent, it increases in age, with the oldest groundwater occurring in the western parts. This means that in order to have travelled almost 1000 km from the source of recharge in 1 million years, the groundwater flowing through the Great Artesian Basin travels at an average rate of about 1 metre per year.

Recent research has demonstrated that evaporation of groundwater can play a significant role in the local water cycle, especially in arid regions.[4]

Reflective carpet trapping soil vapor

Scientists in Saudi Arabia have proposed plans to recapture and recycle this evaporative moisture for crop irrigation. In the opposite photo, a 50-centimeter-square reflective carpet, made of small adjacent plastic cones, was placed in a plant-free dry desert area for five months, without rain or irrigation. It managed to capture and condense enough ground vapor to bring to life naturally buried seeds underneath it, with a green area of about 10% of the carpet area. It is expected that, if seeds were put down before placing this carpet, a much wider area would become green.[5]

Issues

Overview

Certain problems have beset the use of groundwater around the world. Just as river waters have been over-used and polluted in many parts of the world, so too have aquifers. The big difference is that aquifers are out of sight. The other major problem is that water management agencies, when calculating the "sustainable yield" of aquifer and river water, have often counted the same water twice, once in the aquifer, and once in its connected river. This problem, although understood for centuries, has persisted, partly through inertia within government agencies. In Australia, for example, prior to the statutory reforms initiated by the Council of Australian Governments water reform framework in the 1990s, many Australian States managed groundwater and surface water through separate government agencies, an approach beset by rivalry and poor communication.

In general, the time lags inherent in the dynamic response of groundwater to development have been ignored by water management agencies, decades after scientific understanding of the issue was consolidated. In brief, the effects of groundwater overdraft (although undeniably real) may take decades or centuries to manifest themselves. In a classic study in 1982, Bredehoeft and colleagues[6] modelled a situation where groundwater extraction in an intermontane basin withdrew the entire annual recharge, leaving ‘nothing’ for the natural groundwater-dependent vegetation community. Even when the borefield was situated close to the vegetation, 30% of the original vegetation demand could still be met by the lag inherent in the system after 100 years. By year 500, this had reduced to 0%, signalling complete death of the groundwater-dependent vegetation. The science has been available to make these calculations for decades; however, in general water management agencies have ignored effects that will appear outside the rough timeframe of political elections (3 to 5 years). Marios Sophocleous[6] argued strongly that management agencies must define and use appropriate timeframes in groundwater planning. This will mean calculating groundwater withdrawal permits based on predicted effects decades, sometimes centuries in the future. As water moves through the landscape, it collects soluble salts, mainly sodium chloride. Where such water enters the atmosphere through evapotranspiration, these salts are left behind. In irrigation districts, poor drainage of soils and surface aquifers can result in water tables' coming to the surface in low-lying areas. Major land degradation problems of soil salinity and waterlogging result,[7] combined with increasing levels of salt in surface waters. As a consequence, major damage has occurred to local economies and environments.[8]

Four important effects are worthy of brief mention. First, flood mitigation schemes, intended to protect infrastructure built on floodplains, have had the unintended consequence of reducing aquifer recharge associated with natural flooding. Second, prolonged depletion of groundwater in extensive aquifers can result in land subsidence, with associated infrastructure damage – as well as, third, saline intrusion.[9] Fourth, draining acid sulphate soils, often found in low-lying coastal plains, can result in acidification and pollution of formerly freshwater and estuarine streams.[10]

Another cause for concern is that groundwater drawdown from over-allocated aquifers has the potential to cause severe damage to both terrestrial and aquatic ecosystems – in some cases very conspicuously but in others quite imperceptibly because of the extended period over which the damage occurs.[11]

Overdraft

Wetlands contrast the arid landscape around Middle Spring, Fish Springs National Wildlife Refuge, Utah

Groundwater is a highly useful and often abundant resource. However, over-use, or overdraft, can cause major problems to human users and to the environment. The most evident problem (as far as human groundwater use is concerned) is a lowering of the water table beyond the reach of existing wells. As a consequence, wells must be drilled deeper to reach the groundwater; in some places (e.g., California, Texas, and India) the water table has dropped hundreds of feet because of extensive well pumping. In the Punjab region of India, for example, groundwater levels have dropped 10 meters since 1979, and the rate of depletion is accelerating.[12] A lowered water table may, in turn, cause other problems such as groundwater-related subsidence and saltwater intrusion.

Groundwater is also ecologically important. The importance of groundwater to ecosystems is often overlooked, even by freshwater biologists and ecologists. Groundwaters sustain rivers, wetlands, and lakes, as well as subterranean ecosystems within karst or alluvial aquifers.

Not all ecosystems need groundwater, of course. Some terrestrial ecosystems – for example, those of the open deserts and similar arid environments – exist on irregular rainfall and the moisture it delivers to the soil, supplemented by moisture in the air. While there are other terrestrial ecosystems in more hospitable environments where groundwater plays no central role, groundwater is in fact fundamental to many of the world’s major ecosystems. Water flows between groundwaters and surface waters. Most rivers, lakes, and wetlands are fed by, and (at other places or times) feed groundwater, to varying degrees. Groundwater feeds soil moisture through percolation, and many terrestrial vegetation communities depend directly on either groundwater or the percolated soil moisture above the aquifer for at least part of each year. Hyporheic zones (the mixing zone of streamwater and groundwater) and riparian zones are examples of ecotones largely or totally dependent on groundwater.

A possible solution to over-use of groundwater in India

As ageing large-scale surface irrigation schemes have become increasingly inefficient, and farmers have begun growing a wider range of crops requiring water on demand, the number of groundwater wells in India has exploded.[13] In 1960, there were fewer than 100,000 such wells; by 2006 the figure had risen to nearly 12 million.[14] In India, a possible solution to over-use of groundwater is emerging, known as 'groundwater recharge'. It involves capturing rainwater that would otherwise run off, and using it to refill aquifers. Since 2000, the International Water Management Institute (IWMI) has been working with the Indian authorities to help improve the availability of water for agriculture in India. In 2006, India’s finance minister invited IWMI to submit policy recommendations based on its research on groundwater depletion. One of the key recommendations was to instigate a programme of recharging groundwater across the 65% of India that has hard-rock aquifers. As a result, the Indian government allocated Rs 1800 crore (US$400million) to fund dug-well recharge projects (a dug-well is a wide, shallow well, often lined with concrete) in 100 districts within seven states where water stored in hard-rock aquifers has been over-exploited. These geological formations have a much lower capacity to store rainwater than alluvial areas with porous sand or clay rocks, hence being given priority. The money is sufficient to fund seven million structures to be installed on dug-wells to divert monsoon runoff. The structures include a de-siltation chamber, plus pipes to collect surplus rainwater and divert de-silted water from the chamber to the well.[15] As of the end of November 2009, funds amounting to Rs. 216.98 crore (including Rs. 199.98 crore as subsidy to beneficiaries and 17 crore for IEC/Capacity Building activities) had been released to the concerned states. Subsidies had been released to 566,637 beneficiaries.[16]

Subsidence

Subsidence occurs when too much water is pumped out from underground, deflating the space below the above-surface, and thus causing the ground to collapse. The result can look like craters on plots of land. This occurs because, in its natural equilibrium state, the hydraulic pressure of groundwater in the pore spaces of the aquifer and the aquitard supports some of the weight of the overlying sediments. When groundwater is removed from aquifers by excessive pumping, pore pressures in the aquifer drop and compression of the aquifer may occur. This compression may be partially recoverable if pressures rebound, but much of it is not. When the aquifer gets compressed, it may cause land subsidence, a drop in the ground surface. The city of New Orleans, Louisiana is actually below sea level today, and its subsidence is partly caused by removal of groundwater from the various aquifer/aquitard systems beneath it. In the first half of the 20th century, the city of San Jose, California dropped 13 feet from land subsidence caused by overpumping; this subsidence has been halted with improved groundwater management.

Seawater intrusion

In general, in very humid or undeveloped regions, the shape of the water table mimics the slope of the surface. The recharge zone of an aquifer near the seacoast is likely to be inland, often at considerable distance. In these coastal areas, a lowered water table may induce sea water to reverse the flow toward the land. Sea water moving inland is called a saltwater intrusion. In alternative fashion, salt from mineral beds may leach into the groundwater of its own accord.

Pollution

Iron oxide staining caused by reticulation from an unconfined aquifer in karst topography. Perth, Western Australia.


Water pollution of groundwater, from pollutants released to the ground that can work their way down into groundwater, can create a contaminant plume within an aquifer. Movement of water and dispersion within the aquifer spreads the pollutant over a wider area, its advancing boundary often called a plume edge, which can then intersect with groundwater wells or daylight into surface water such as seeps and springs, making the water supplies unsafe for humans and wildlife. The interaction of groundwater contamination with surface waters is analyzed by use of hydrology transport models.

The stratigraphy of the area plays an important role in the transport of these pollutants. An area can have layers of sandy soil, fractured bedrock, clay, or hardpan. Areas of karst topography on limestone bedrock are sometimes vulnerable to surface pollution from groundwater. Earthquake faults can also be entry routes for downward contaminant entry. Water table conditions are of great importance for drinking water supplies, agricultural irrigation, waste disposal (including nuclear waste), wildlife habitat, and other ecological issues.[17]

In the US, upon commercial real estate property transactions both groundwater and soil are the subjects of scrutiny, with a Phase I Environmental Site Assessment normally being prepared to investigate and disclose potential pollution issues.[18] In the San Fernando Valley of California, real estate contracts for property transfer below the Santa Susana Field Laboratory (SSFL) and eastward have clauses releasing the seller from liability for groundwater contamination consequences from existing or future pollution of the Valley Aquifer.

Love Canal was one of the most widely known examples of groundwater pollution. In 1978, residents of the Love Canal neighborhood in upstate New York noticed high rates of cancer and an alarming number of birth defects. This was eventually traced to organic solvents and dioxins from an industrial landfill that the neighborhood had been built over and around, which had then infiltrated into the water supply and evaporated in basements to further contaminate the air. Eight hundred families were reimbursed for their homes and moved, after extensive legal battles and media coverage.

Another example of widespread groundwater pollution is in the Ganges Plain of northern India and Bangladesh where severe contamination of groundwater by naturally occurring arsenic affects 25% of water wells in the shallower of two regional aquifers. The pollution occurs because aquifer sediments contain organic matter that generates anaerobic conditions in the aquifer. These conditions result in the microbial dissolution of iron oxides in the sediment and, thus, the release of the arsenic, normally strongly bound to iron oxides, into the water. As a consequence, arsenic-rich groundwater is often iron-rich, although secondary processes often obscure the association of dissolved arsenic and dissolved iron.[citation needed]

Government regulations

In November 2006, the Environmental Protection Agency published the Ground Water Rule in the United States Federal Register. The EPA was worried that the ground water system would be vulnerable to contamination from fecal matter. The point of the rule was to keep microbial pathogens out of public water sources.[19] The 2006 Ground Water Rule was an amendment of the 1996 Safe Drinking Water Act.

See also

Template:Colbegin

  • Groundwater models
  • Groundwater flow
  • Baseflow
  • Seep (hydrology)
  • Spring (hydrosphere)
  • Water well
  • Optimum water content for tillage
  • Environmental Persistent Pharmaceutical Pollutant EPPP

Template:Colend

References
ISBN links support NWE through referral fees

  1. Richard Greenburg (2005). The Ocean Moon: Search for an Alien Biosphere. Springer Praxis Books. 
  2. Learn More: Groundwater. Columbia Water Center. Retrieved 2009-09-15.
  3. Groundwater flow.svg.
  4. {{#invoke:citation/CS1|citation |CitationClass=thesis }}
  5. Al-Kasimi, S. M. (2002). "Existence of Ground Vapor-Flux Up-Flow: Proof & Utilization in Planting The Desert Using Reflective Carpet". Proceedings of the Saudi Sixth Engineering Conference, 105-119.
  6. 6.0 6.1 (2002). Interactions between groundwater and surface water: the state of the science. Hydrogeology Journal 10: 52–67.
  7. Free articles and software on drainage of waterlogged land and soil salinity control. Retrieved 2010-07-28.
  8. (1993). Uncertainty, Resource Exploitation, and Conservation: Lessons from History. Science 260 (5104): 17–36.
  9. Zektser et al.
  10. (2001). Water quality and macroinvertebrate response to acidification following intensified summer droughts in a Western Australian wetland. Marine and Freshwater Research 52 (7): 1015.
  11. (2004). Environmental impacts of groundwater overdraft: selected case studies in the southwestern United States. Environmental Geology 47 (3): 396–404.
  12. Upmanu Lall. Punjab: A tale of prosperity and decline. Columbia Water Center. Retrieved 2009-09-11.
  13. Mukherji, A. Revitalising Asia’s Irrigation: To sustainably meet tomorrow’s food needs 2009, IWMI and FAO
  14. Chapter 10: The Groundwater Recharge Movement in India, By Sakthivadivel, R. in The Agricultural Groundwater Revolution, Ed. Giordano, M. and Villholth, K, CABI Publications, 2007
  15. Influencing irrigation policy in India, Success Story 6, 2010, International Water Management Institute, Colombo, Sri Lanka
  16. Initiatives in Water Resources, Indian Current Affairs, December 30, 2009, page accessed 5 May 2011
  17. Groundwater Sampling; http://www.groundwatersampling.org/
  18. EPA; http://water.epa.gov/type/groundwater/index
  19. Ground Water Rule (GWR) | Ground Water Rule | US EPA. Water.epa.gov. Retrieved on 2011-06-09.
  • Meinzer, O. E., 1923, Outline of ground-water hydrology, with definitions: U.S. Geol. Survey Water-Supply Paper 494, 71 p
  • Meinzer, O. E., ed., 1949, Physics of the earth, pt. 9, Hydrology: New York, Dover Pub., 712 p.

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