Groundwater - Knowledge (XXG)

1487: 948: 1335: 65: 865: 1683: 1312: 620:. 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 825: 1032:

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.

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practice is underpinned by an assumption that untreated groundwater is typically suitable for drinking due to the relative microbiological safety of groundwater compared to surface water; however, chemistry risks are largely disregarded. Chemical contaminants occur widely in groundwaters that are used for drinking but are not regularly monitored. Example priority parameters are fluoride, arsenic, nitrate, or salinity.

355: 5504: 521: 576: 681: 439:, 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. 3176: 3037: 2735: 2633: 566:), which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could lead to the formation of a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer. 960: 1295:. In the case of homogeneous aquifers, seawater intrusion forms a saline wedge below a transition zone to fresh groundwater, flowing seaward on the top. These changes can have other effects on the land above the groundwater. For example, coastal groundwater in California would rise in many aquifers, increasing risks of flooding and 363: 648:

The volume of groundwater in an aquifer can be estimated by measuring water levels in local wells and by examining geologic records from well-drilling to determine the extent, depth and thickness of water-bearing sediments and rocks. Before an investment is made in production wells, test wells may be

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supply, which is about 0.76% of the entire world's water, including oceans and permanent ice. About 99% of the world's liquid fresh water is groundwater. 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.

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which in turn affect groundwater in several ways: There can be a decline in groundwater storage, and reduction in groundwater recharge and water quality deterioration due to extreme weather events. In the tropics intense precipitation and flooding events appear to lead to more groundwater recharge.

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Aquifers 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 12

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Reliance on groundwater is increasing in Sub-Saharan Africa as development programs work towards improving water access and strengthening resilience to climate change. In lower-income areas, groundwater supplies are typically installed without water quality treatment infrastructure or services. This

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supply, particularly in dry regions where surface water availability is limited. Globally, more than one-third of the water used originates from underground. In the mid-latitude arid and semi-arid regions lacking sufficient surface water supply from rivers and reservoirs, groundwater is critical for

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In general, the irrigation of 20% of farming land (with various types of water sources) accounts for the production of 40% of food production. Irrigation techniques across the globe includes canals redirecting surface water, groundwater pumping, and diverting water from dams. Aquifers are critically

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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

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have some form of aquifer underlying them, sometimes at significant depths. In some cases, these aquifers are rapidly being depleted by the human population. Such over-use, over-abstraction or overdraft can cause major problems to human users and to the environment. The most evident problem (as far

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and seepage to the oceans. Due to its slow rate of turnover, groundwater storage is generally much larger (in volume) compared to inputs than it is for surface water. This difference makes it easy for humans to use groundwater unsustainably for a long time without severe consequences. Nevertheless,

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properties. For this reason, salinity of groundwater is often highly variable over space. This contributes to highly variable groundwater security risks even within a specific region. Salinity in groundwater makes the water unpalatable and unusable and often occurs in coastal areas, for example in

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may also increase indirectly due to climate change: More frequent and intense storms can pollute groundwater by mobilizing contaminants, for example fertilizers, wastewater or human excreta from pit latrines. Droughts reduce river dilution capacities and groundwater levels, increasing the risk of

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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

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Global freshwater withdrawal was probably around 600 km per year in 1900 and increased to 3,880 km per year in 2017. The rate of increase was especially high (around 3% per year) during the period 1950–1980, partly due to a higher population growth rate, and partly to rapidly increasing

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Domestic laws and regulations regulate access to groundwater as well as human activities that impact the quality of groundwater. Legal frameworks also need to include protection of discharge and recharge zones and of the area surrounding water supply wells, as well as sustainable yield norms and

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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

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Groundwater management is action-oriented, focusing on practical implementation activities and day-to-day operations. Because groundwater is often perceived as a private resource (that is, closely connected to land ownership, and in some jurisdictions treated as privately owned), regulation and

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However, the exact impacts of climate change on groundwater are still under investigation. This is because scientific data derived from groundwater monitoring is still missing, such as changes in space and time, abstraction data and "numerical representations of groundwater recharge processes".

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Municipal 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 groundwater from deep, confined aquifers provides more protection from surface water

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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

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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

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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 metres) and have some recharge by fresh water. This recharge is typically from rivers or meteoric water (precipitation) that

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sustaining global ecology and meeting societal needs of drinking water and food production. The demand for groundwater is rapidly increasing with population growth, while climate change is imposing additional stress on water resources and raising the probability of severe drought occurrence.

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Arroyo, Danny; Ordaz, Mario; Ovando-Shelley, Efrain; Guasch, Juan C.; Lermo, Javier; Perez, Citlali; Alcantara, Leonardo; Ramírez-Centeno, Mario S. (2013). "Evaluation of the change in dominant periods in the lake-bed zone of Mexico City produced by ground subsidence through the use of site

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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

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is one of the most water-scarce in the world and groundwater is the most relied-upon water source in at least 11 of the 22 Arab states. Over-extraction of groundwater in many parts of the region has led to groundwater table declines, especially in highly populated and agricultural areas.

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Aquifer systems that are vulnerable to climate change include the following examples (the first four are largely independent of human withdrawals, unlike examples 5 to 8 where the intensity of human groundwater withdrawals plays a key role in amplifying vulnerability to climate change):

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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). Deep groundwater (which is quite distant from the surface recharge) can take a very long time to complete its natural cycle.

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The most common methods to estimate recharge rates are: chloride mass balance (CMB); soil physics methods; environmental and isotopic tracers; groundwater-level fluctuation methods; water balance (WB) methods (including groundwater models (GMs)); and the estimation of baseflow (BF) to

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is the largest groundwater abstractor in the world, containing seven out of the ten countries that extract most groundwater (Bangladesh, China, India, Indonesia, Iran, Pakistan and Turkey). These countries alone account for roughly 60% of the world's total groundwater withdrawal.

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Sea level rise causes the mixing of sea water into the coastal groundwater, rendering it unusable once it amounts to more than 2-3% of the reservoir. Along an estimated 15% of the US coastline, the majority of local groundwater levels are already below the sea level.

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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

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to climate change exploit distributed groundwater storage and the capacity of aquifer systems to store seasonal or episodic water surpluses. They incur substantially lower evaporative losses than conventional infrastructure, such as surface dams. For example, in

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due to climate change has induced seawater intrusion into coastal aquifers around the world, particularly in low-lying areas and small islands. However, groundwater abstraction is usually the main reason for seawater intrusion, rather than sea level rise (see in

2766:. In Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S.L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L.; Gomis, M.I.; Huang, M.; Leitzell, K.; Lonnoy, E.; Matthews, J.B.R.; Maycock, T.K.; Waterfield, T.; Yelekçi, O.; Yu, R.; Zhou, B. (eds.). 860:

project has pumped large amounts of groundwater from aquifers beneath the Sahara to populous areas near the coast. Though this has saved Libya money over the alternative, seawater desalination, the aquifers are likely to run dry in 60 to 100 years.

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MacDonald, Alan M; Lark, R Murray; Taylor, Richard G; Abiye, Tamiru; Fallas, Helen C; Favreau, Guillaume; Goni, Ibrahim B; Kebede, Seifu; Scanlon, Bridget; Sorensen, James P R; Tijani, Moshood; Upton, Kirsty A; West, Charles (2021-03-01).

1098:. 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. 722:, and surface water for the other two thirds. Groundwater provides drinking water to at least 50% of the global population. About 2.5 billion people depend solely on groundwater resources to satisfy their basic daily water needs. 725:

A similar estimate was published in 2021 which stated that "groundwater is estimated to supply between a quarter and a third of the world's annual freshwater withdrawals to meet agricultural, industrial and domestic demands."

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drilled to measure the depths at which water is encountered and collect samples of soils, rock and water for laboratory analyses. Pumping tests can be performed in test wells to determine flow characteristics of the aquifer.

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Douville, H.; Raghavan, K.; Renwick, J.; Allan, R.P.; Arias, P.A.; Barlow, M.; Cerezo-Mota, R.; Cherchi, A.; Gan, T.Y.; Gergis, J.; Jiang, D.; Khan, A.; Pokam Mba, W.; Rosenfeld, D.; Tierney, J.; Zolina, O. (2021).

225:, and California annually withdraws the largest amount of groundwater of all the states. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, including the 434:

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

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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.,

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Sommer, Bea; Horwitz, Pierre; Sommer, Bea; Horwitz, Pierre (2001). "Water quality and macroinvertebrate response to acidification following intensified summer droughts in a Western Australian wetland".

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Groundwater may or may not be a safe water source. In fact, there is considerable uncertainty with groundwater in different hydrogeologic contexts: the widespread presence of contaminants such as

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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

3899: 1276:. If too much groundwater is pumped near the coast, salt-water may intrude into freshwater aquifers causing contamination of potable freshwater supplies. Many coastal aquifers, such as the 1113:

in Thailand, have experienced surface subsidence; Mexico City, built on a former lake bed, has experienced rates of subsidence of up to 40 centimetres (1 foot 4 inches) per year.

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is less visible and more difficult to clean up than pollution in rivers and lakes. Groundwater pollution most often results from improper disposal of wastes on land. Major sources include

1502:. There is an observed declined in groundwater storage in many parts of the world. This is due to more groundwater being used for irrigation activities in agriculture, particularly in 1701:

processes enable groundwater management, planning and policy implementation. It takes place at multiple scales and geographic levels, including regional and transboundary scales.

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and surface water, such as seeps and springs, making the water supplies unsafe for humans and wildlife. The movement of the plume, called a plume front, may be analyzed through a

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important in agriculture. Deep aquifers in arid areas have long been water sources for irrigation. A majority of extracted groundwater, 70%, is used for agricultural purposes.

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Polemio, M.; Dragone, V.; Limoni, P.P. (2009). "Monitoring and methods to analyse the groundwater quality degradation risk in coastal karstic aquifers (Apulia, Southern Italy)".

1000:, for example, groundwater levels have dropped 10 meters since 1979, and the rate of depletion is accelerating. A lowered water table may, in turn, cause other problems such as 1055:

if local groundwater levels decline by a few meters, or – as with many areas and possibly more than half of major aquifers – continue to decline.

2896: 4329:. In Pörtner, H.-O.; Roberts, D.C.; Tignor, M.; Poloczanska, E.S.; Mintenbeck, K.; Alegría, A.; Craig, M.; Langsdorf, S.; Löschke, S.; Möller, V.; Okem, A.; Rama, B. (eds.). 4322:

Caretta, M.A.; Mukherji, A.; Arfanuzzaman, M.; Betts, R.A.; Gelfan, A.; Hirabayashi, Y.; Lissner, T.K.; Liu, J.; Lopez Gunn, E.; Morgan, R.; Mwanga, S.; Supratid, S. (2022).

4064:. Lecture notes International Course on Land Drainage, International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. Download from : 1663:

In pioneering nations, such as the Netherlands and Sweden, the ground/groundwater is increasingly seen as just one component (a seasonal source, sink or thermal 'buffer') in

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can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as

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is one of the largest confined aquifer systems in the world, extending for almost 2 million km. By analysing the trace elements in water sourced from deep underground,

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Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change

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top–down governance and management are difficult. Governments need to fully assume their role as resource custodians in view of the common-good aspects of groundwater.

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groundwater development, particularly for irrigation. The rate of increase is (as per 2022) approximately 1% per year, in tune with the current population growth rate.

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Global groundwater depletion has been calculated to be between 100 and 300 km per year. This depletion is mainly caused by "expansion of irrigated agriculture in

1427:. Movement of water and dispersion within the aquifer spreads the pollutant over a wider area. Its advancing boundary, often called a plume edge, can intersect with 491:

surface. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally (through the

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Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change

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Aobpaet, Anuphao; Cuenca, Miguel Caro; Hooper, Andrew; Trisirisatayawong, Itthi (2013). "InSAR time-series analysis of land subsidence in Bangkok, Thailand".

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Zektser, S.; LoaIciga, H. A.; Wolf, J. T. (2004). "Environmental impacts of groundwater overdraft: selected case studies in the southwestern United States".

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abstraction controls, and conjunctive use regulations. In some jurisdictions, groundwater is regulated in conjunction with surface water, including rivers.

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Reducing the Greenhouse Gas Emissions of Water and Sanitation Services: Overview of emissions and their potential reduction illustrated by utility know-how

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damage occurs. The importance of groundwater to ecosystems is often overlooked, even by freshwater biologists and ecologists. Groundwaters sustain rivers,

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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.

2156: 1514:. Direct redistribution of water by human activities amounting to ~24,000 km per year is about double the global groundwater recharge each year. 929:. Fourth, draining acid sulphate soils, often found in low-lying coastal plains, can result in acidification and pollution of formerly freshwater and 898:

The anthropogenic effects on groundwater resources are mainly due to groundwater pumping and the indirect effects of irrigation and land use changes.

657:-filling sediments in major river valleys and geologically subsiding structural basins are included among the most productive sources of groundwater. 1175:

result, combined with increasing levels of salt in surface waters. As a consequence, major damage has occurred to local economies and environments.

3144:"Water chemistry poses health risks as reliance on groundwater increases: A systematic review of hydrogeochemistry research from Ethiopia and Kenya" 715:. Groundwater accounts for about half of the world's drinking water, 40% of its irrigation water, and a third of water for industrial purposes. 4382: 4036:, In: Annual Report 1988 of the International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, pp. 18–34 1543:

For the higher altitudes regions, the reduced duration and amount of snow may lead to reduced recharge of groundwater in spring. The impacts of

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over the long term the average rate of seepage above a groundwater source is the upper bound for average consumption of water from that source.

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Under the influence of continuous evaporation, the salt concentration of the aquifer water may increase continually and eventually cause an

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Akhter, Tanjila; Naz, Maheen; Salehin, Mashfiqus; Arif, Sharif Tanjim; Hoque, Sonia Ferdous; Hope, Robert; Rahman, Mohammad Rezaur (2023).

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near Miami and the New Jersey Coastal Plain aquifer, have problems with saltwater intrusion as a result of overpumping and sea level rise.

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farmland. In coastal areas, human use of a groundwater source may cause the direction of seepage to ocean to reverse which can also cause

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First, flood mitigation schemes, intended to protect infrastructure built on floodplains, have had the unintended consequence of reducing

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contamination. Some wells, termed "collector wells", are specifically designed to induce infiltration of surface (usually river) water.

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of water and the insulating effect of soil and rock can mitigate the effects of climate and maintain groundwater at a relatively steady

380:: inputs, outputs and storage. The natural input to groundwater is seepage from surface water. The natural outputs from groundwater are 1536:

groundwater recharge in many environments. But more intense drought periods could result in soil drying-out and compaction which would

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Groundwater plays a central role in sustaining water supplies and livelihoods in sub-Saharan Africa. In some cases, groundwater is an

558:). Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called 5357: 3898:

Nicholls, R. J.; Hanson, S.; Herweijer, C.; Patmore, N.; Hallegatte, S.; CorfeeMorlot, J.; Chateau, Jean; Muir-Wood, Robert (2008).

1979: 3683:"The role of deep processes in late 20th century subsidence of New Orleans and coastal areas of southern Louisiana and Mississippi" 2956: 1498:

The impacts of climate change on groundwater may be greatest through its indirect effects on irrigation water demand via increased

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districts, poor drainage of soils and surface aquifers can result in water tables' coming to the surface in low-lying areas. Major

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Tosi, Luigi; Teatini, Pietro; Strozzi, Tazio; Da Lio, Cristina (2014). "Relative Land Subsidence of the Venice Coastland, Italy".

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could have different impacts on groundwater storage: The expected more intense (but fewer) major rainfall events could lead to

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Not all ecosystems need groundwater, of course. Some terrestrial ecosystems – for example, those of the open

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Nowicki, Saskia; Birhanu, Behailu; Tanui, Florence; Sule, May N.; Charles, Katrina; Olago, Daniel; Kebede, Seifu (2023).

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bodies. This can be a serious problem, especially in coastal areas and other areas where aquifer pumping is excessive.

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associated with natural flooding. Second, prolonged depletion of groundwater in extensive aquifers can result in land

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In India, 65% of the irrigation is from groundwater and about 90% of extracted groundwater is used for irrigation.

5507: 5391: 5335: 4427: 4365: 3740:"Land Subsidence along the Delta-Mendota Canal in the Northern Part of the San Joaquin Valley, California, 2003–10" 2181:"Non-renewable groundwater resources: a guidebook on socially-sustainable management for water-policy makers; 2006" 1816: 1219:

in such a case, annually an amount of drainage water is to be discharged from the aquifer by means of a subsurface

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can reduce the suitability of groundwater as a drinking water source. Arsenic and fluoride have been considered as

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have been able to determine that water extracted from these aquifers can be more than 1 million years old.

4907: 1861: 1851: 1831: 1821: 1781: 1682: 1455:, and the nature of the contaminants. Different mechanisms have influence on the transport of pollutants, e.g. 1273: 864: 337: 3400:

Bagheri, Rahim; Nosrati, Azad; Jafari, Hadi; Eggenkamp, Hermanus Gerardus M.; Mozafari, Morteza (5 May 2019).

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Fleury, P.; Bakalowicz, M.; De Marsily, G. (2007). "Submarine springs and coastal karst aquifers: a review".

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Reliance on groundwater will only increase, mainly due to growing water demand by all sectors combined with

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This makes it an important resource that can act as a natural storage that can buffer against shortages of

5485: 5328: 5200: 3402:"Overexploitation hazards and salinization risks in crucial declining aquifers, chemo-isotopic approaches" 3401: 1876: 1856: 1846: 1791: 1420: 1102: 613: 4217:"Groundwater level observations in 250,000 coastal US wells reveal scope of potential seawater intrusion" 562:. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude (or 5548: 5282: 5277: 5072: 5013: 3380: 2532: 1841: 1796: 1786: 1691: 1574: 1354: 1327: 1216: 1132:

If the surface water source is also subject to substantial evaporation, a groundwater source may become

495:) and through anthropogenic processes (i.e., "artificial groundwater recharge"), where rainwater and/or 233: 2265:

Gleeson, Tom; Befus, Kevin M.; Jasechko, Scott; Luijendijk, Elco; Cardenas, M. Bayani (February 2016).

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have collected data that demonstrates 21 of Earth's 37 major aquifers are undergoing depletion. In the

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Liu, Pang-Wei; Famiglietti, James S.; Purdy, Adam J.; Adams, Kyra H.; et al. (19 December 2022).

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Jasechko, Scott J.; Perrone, Debra; Seybold, Hansjörg; Fan, Ying; Kirchner, James W. (26 June 2020).

4189: 4146: 4095: 3971: 3861: 3809: 3694: 3640: 3570: 3483: 3413: 3333: 3271: 3069: 3000: 2989:"Divergent effects of climate change on future groundwater availability in key mid-latitude aquifers" 2566: 2372: 2361:"Mapping groundwater recharge in Africa from ground observations and implications for water security" 2278: 2231: 2041: 2025: 1871: 1826: 1801: 1750: 1390: 1183: 456: 449: 436: 420: 401: 381: 132: 128: 3053:

Cuthbert MO, Taylor RG, Favreau G, Todd MC, Shamsudduha M, Villholth KG, et al. (August 2019).

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in many environments. Unconsolidated to poorly cemented alluvial materials that have accumulated as

5471: 5379: 5367: 5257: 5210: 5018: 4941: 4667: 4458: 2339: 1866: 1836: 1414: 1315: 1284: 1256: 1005: 926: 857: 741: 328:. Sometimes it is useful to make a distinction between groundwater that is closely associated with 269: 241: 237: 191: 3900:"Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposure Estimates" 2528: 1287:. It is a natural phenomenon but can also be caused or worsened by anthropogenic factors, such as 853:

aquifers are used to provide irrigation and drinking water to urban areas. In Libya, for example,

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The United Nations World Water Development Report 2022: Groundwater: Making the invisible visible

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Bethke, Craig M.; Johnson, Thomas M. (May 2008). "Groundwater Age and Groundwater Age Dating".

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Seawater intrusion is the flow or presence of seawater into coastal aquifers; it is a case of

1240: 1236: 1145: 588: 245: 195: 156: 3113:"Ethiopia's future is tied to water -- a vital yet threatened resource in a changing climate" 3055:"Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa" 1401:. Pollution (or contamination) can also occur from naturally occurring contaminants, such as 5403: 5362: 5345: 5232: 5130: 4662: 4566: 4450: 4336: 4244: 4236: 4197: 4154: 4103: 4082:

Befus, K. M.; Barnard, P. L.; Hoover, D. J.; Finzi Hart, J. A.; Voss, C. I. (October 2020).

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aquifers in rapidly expanding low-income cities and large displaced and informal communities

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For coastal cities, subsidence can increase the risk of other environmental issues, such as

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Fresh-water aquifers, especially those with limited recharge by snow or rain, also known as

1048: 1021: 918: 836: 719: 600: 210:'s subsurface contains some water, which may be mixed with other fluids in some instances. 136: 3739: 2243: 824: 5420: 5386: 5272: 5252: 5162: 4811: 4777: 4711: 4508: 4493: 3180: 2825: 2637: 2505: 2488: 2346: 1908: – A goal of water management to harness water-related opportunities and manage risks 1899: 1718: 1674:, the process of storing carbon to curb accumulation of carbon dioxide in the atmosphere. 1660:. Groundwater is an agent in the storage, movement, and extraction of geothermal energy. 1629: 1564: 1386: 1362: 1187: 1152: 854: 665: 496: 273: 214: 203: 2960: 4232: 4193: 4150: 4099: 3975: 3865: 3813: 3698: 3644: 3574: 3533:"The largest assessment of global groundwater wells finds many are at risk of drying up" 3487: 3417: 3337: 3275: 3073: 3004: 2570: 2376: 2282: 2235: 2045: 5558: 5461: 5408: 5318: 5237: 5222: 5217: 5169: 5057: 4853: 4801: 4784: 4618: 4249: 4216: 3292: 3259: 3021: 2988: 1905: 1551: 1507: 1481: 1296: 1292: 1288: 1262: 1117: 1059: 1052: 1033: 796: 704: 412: 317: 289: 277: 3936:"Free articles and software on drainage of waterlogged land and soil salinity control" 3558: 3471: 988:) the water table has dropped hundreds of feet because of extensive well pumping. The 718:

Another estimate stated that globally groundwater accounts for about one third of all

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in the world is groundwater. A unit of rock or an unconsolidated deposit is called an

5522: 5425: 5262: 5152: 5109: 4890: 4767: 4653: 4603: 4467: 4123: 3837: 3660: 3606: 3511: 3361: 3260:"Groundwater depletion in California's Central Valley accelerates during megadrought" 3216: 3097: 2678: 2649:

Alix, Alexandre; Bellet, Laurent; Trommsdorff, Corinne; Audureau, Iris, eds. (2022).

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can be spread via a groundwater well which is contaminated with fecal pathogens from

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Groundwater is the most accessed source of freshwater around the world, including as

638: 584: 580: 468: 377: 329: 261: 222: 218: 179: 4166: 4084:"Increasing threat of coastal groundwater hazards from sea-level rise in California" 4083: 3724: 3449: 3321: 3160: 3143: 2578: 1616:

Using more groundwater, particularly in Sub-Saharan Africa, is seen as a method for

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Drainage for Agriculture: Drainage and hydrology/salinity - water and salt balances

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and livelihood resilience. Bangladesh is a vulnerable country for this issue, and

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and pesticides used in agriculture, industrial waste lagoons, tailings and process

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7-year research project on the "Potential of Groundwater for the Poor" (2013–2020)

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Wu WY, Lo MH, Wada Y, Famiglietti JS, Reager JT, Yeh PJ, et al. (July 2020).

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down into the underground by supplemental irrigation from wells run the risk of

1120:. For example, Bangkok is expected to have 5.138 million people exposed to 891: 633: 617: 492: 488: 476: 408: 349: 325: 265: 226: 199: 148: 124: 108: 73: 4240: 4030:

Effectiveness and Social/Environmental Impacts of Irrigation Projects: a Review

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areas in semi-arid zones with reuse of the unavoidable irrigation water losses

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Groundwater is a highly useful and often abundant resource. Most land areas on

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Groundwater: Hydrogeochemistry, Environmental Impacts and Management Practices

4158: 4107: 3652: 3345: 3208: 3081: 2860: 2848: 2777: 1952:"What is Groundwater? | International Groundwater Resources Assessment Centre" 1698: 1568: 1460: 1428: 1394: 1374: 1347: 1268:

metres (40 ft) for every 0.3 m (1 ft) of freshwater head above

1179: 1160: 1141: 1095: 977: 922: 819: 708: 685: 680: 301: 253: 249: 183: 160: 4293: 4115: 3881: 3829: 3716: 3590: 3433: 3353: 2728: 2514: 2394: 2333: 2298: 2251: 2061: 1598:

intensively pumped aquifer systems for groundwater-fed irrigation in drylands

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aquifer systems in continental northern latitudes or alpine and polar regions

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are released to the ground and make their way into groundwater. This type of

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to groundwater. Recharge is the primary method through which water enters an

260:, oil field brine pits, leaking underground oil storage tanks and pipelines, 5313: 5195: 5003: 4998: 4976: 4865: 4858: 4677: 4672: 4579: 4556: 4068: 3957:"Uncertainty, Resource Exploitation, and Conservation: Lessons from History" 3582: 3495: 2465: 2084:"Humans pump so much groundwater that Earth's axis has shifted, study finds" 1995: 1951: 1921: 1456: 1452: 1370: 1358: 1269: 1137: 925:, with associated infrastructure damage – as well as, third, 661: 621: 524:

Schematic of an aquifer showing confined zones, groundwater travel times, a

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in the case that climate change causes more intense or frequent droughts.

17: 5440: 5008: 4934: 4875: 4870: 4818: 4728: 4699: 4692: 4682: 4613: 4587: 4583: 4575: 3914: 3707: 3682: 2801: 2053: 1893: 1742: 1503: 1482:

Water security § Reduced water quality due to climate change impacts

1406: 1378: 1244: 1133: 768: 764: 734: 596: 313: 257: 120: 100: 3322:"Deeper well drilling an unsustainable stopgap to groundwater depletion" 1151:

As water moves through the landscape, it collects soluble salts, mainly

959: 5308: 5104: 5099: 5045: 4951: 4880: 4723: 4524: 3991: 3175: 3036: 2937: 2734: 2632: 2553:

Bense, V.F.; Gleeson, T.; Loveless, S.E.; Bour, O.; Scibek, J. (2013).

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and voids in rock become completely saturated with water is called the

112: 104: 69: 4330: 3629:"Review: Regional land subsidence accompanying groundwater extraction" 2767: 2719: 2702: 2211:(First ed.). United States Government Printing Office. p. 4. 775:

at a global level, although priority chemicals will vary by country.

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Typically, groundwater is thought of as water flowing through shallow

5157: 5122: 4946: 4902: 4750: 4548: 4273: 2927: 2910: 2290: 1339: 1028: 832: 810:

percolates into the aquifer through overlying unsaturated materials.

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Human use of groundwater causes environmental problems. For example,

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Groundwater is often cheaper, more convenient and less vulnerable to

4419: 4065: 3244: 5190: 5030: 4956: 4743: 2109:"Rampant Groundwater Pumping Has Changed the Tilt of Earth's Axis" 1681: 1491: 1485: 1333: 1310: 1223:

and disposed of through a safe outlet. The drainage system may be

997: 985: 981: 972: 958: 946: 869: 823: 679: 574: 539: 519: 464: 397: 362: 361: 353: 207: 140: 92: 88: 63: 4383:

Groundwater: The world's neglected defence against climate change

2157:"Humans Have Shifted Earth's Axis by Pumping Lots of Groundwater" 1632:, pumping water from groundwater storage can help to improve the 1595:

shallow alluvial aquifers underlying seasonal rivers in drylands,

1197:

or more and the annual irrigation requirement is in the order of

1193:

Surface irrigation water normally contains salts in the order of

131:

from the surface; it may discharge from the surface naturally at

115:

when it can yield a usable quantity of water. The depth at which

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http://hydrogeologistswithoutborders.org/wordpress/1979-english/

1726: 1440: 1243:

with an agro-hydro-salinity component may be instrumental, e.g.

1017: 883: 555: 551: 529: 484: 480: 152: 116: 77: 4423: 1746: 163:. The study of the distribution and movement of groundwater is 5094: 4738: 4397: 951:

Within a long period of groundwater depletion in California's

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