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75-530: The discovery led to a massive post-war staking boom in Yellowknife. Giant Mine entered production in 1948 and ceased operations in 2004. It produced over 7,000,000  ozt (220,000 kg) of gold. Owners of the mine have included Falconbridge (1948–1986 through subsidiary Giant Yellowknife Mines Limited), Pamour of Australia (1986–1990 through subsidiary Giant Yellowknife Mines Limited), and Royal Oak Mines (1990–1999). When Royal Oak went bankrupt in 1999

150-408: A drop in the ground surface. 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

225-402: A former lake bed, has experienced rates of subsidence of up to 40 centimetres (1 foot 4 inches) per year. For coastal cities, subsidence can increase the risk of other environmental issues, such as sea level rise . For example, Bangkok is expected to have 5.138 million people exposed to coastal flooding by 2070 because of these combining factors. If the surface water source

300-1076: A global level, although priority chemicals will vary by country. There is a lot of heterogeneity of hydrogeologic 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 Bangladesh and East and West Africa. 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 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

375-408: 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. Groundwater makes up about thirty percent of the world's fresh water supply, which is about 0.76% of the entire world's water, including oceans and permanent ice. About 99% of

450-519: A long time without severe consequences. Nevertheless, 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. Groundwater is naturally replenished by surface water from precipitation , streams , and rivers when this recharge reaches the water table. 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

525-722: A permanently reduced capacity to hold water. 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 San Joaquin Valley experienced significant subsidence , in some places up to 8.5 metres (28 feet) due to groundwater removal. Cities on river deltas, including Venice in Italy, and Bangkok in Thailand, have experienced surface subsidence; Mexico City, built on

600-412: A total of 237,000 tonnes (233,000 long tons; 261,000 short tons) of deadly arsenic trioxide dust, containing up to 60% organic and inorganic arsenic. The dust was a byproduct of extracting gold from the mineral and was collected and stored in sealed underground chambers from 1951 to 1999. Prior to legislated collection and underground storage in 1951 arsenic was released directly into the atmosphere during

675-399: Is a highly useful and often abundant resource. Most land areas on Earth have some form of aquifer underlying them, sometimes at significant depths. In some cases, these aquifers are rapidly being depleted by the 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 as human groundwater use

750-528: 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 . Typically, groundwater is thought of as water flowing through shallow aquifers, but, in the technical sense, it can also contain soil moisture , permafrost (frozen soil), immobile water in very low permeability bedrock , and deep geothermal or oil formation water. Groundwater

825-466: Is also subject to substantial evaporation, a groundwater source may become saline . This situation can occur naturally under endorheic bodies of water, or artificially under irrigated farmland. In coastal areas, human use of a groundwater source may cause the direction of seepage to ocean to reverse which can also cause soil salinization . As water moves through the landscape, it collects soluble salts, mainly sodium chloride . Where such water enters

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900-632: Is an additional water source that was not used previously. 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 . Fourth, draining acid sulphate soils, often found in low-lying coastal plains, can result in acidification and pollution of formerly freshwater and estuarine streams. Groundwater

975-417: 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. The GRACE satellites have collected data that demonstrates 21 of Earth's 37 major aquifers are undergoing depletion. In

1050-513: Is considered to be sufficiently approximated by 31.10 g in EU directive 80/181/EEC. The Dutch troy system is based on a mark of 8 ounces, the ounce of 20 engels (pennyweights), the engel of 32 as. The mark was rated as 3,798 troy grains or 246.084 grammes. The divisions are identical to the tower system. The pennyweight symbol is dwt . One pennyweight weighs 24 grains, and 20 pennyweights make one troy ounce. Because there were 12 troy ounces in

1125-412: Is fresh water located in the subsurface pore space of soil and rocks . It is also water that is flowing within aquifers below the water table . Sometimes it is useful to make a distinction between groundwater that is closely associated with surface water , and deep groundwater in an aquifer (called " fossil water " if it infiltrated into the ground millennia ago ). Groundwater can be thought of in

1200-427: Is hypothesized to provide lubrication that can possibly influence the movement of faults . It is likely that much of Earth 's subsurface contains some water, which may be mixed with other fluids in some instances. Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water . Therefore, it is commonly used for public drinking water supplies. For example, groundwater provides

1275-545: 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 industrial and household chemicals and garbage landfills , excessive fertilizers and pesticides used in agriculture, industrial waste lagoons, tailings and process wastewater from mines, industrial fracking , oil field brine pits, leaking underground oil storage tanks and pipelines, sewage sludge and septic systems . Additionally, groundwater

1350-544: Is odourless, tasteless and semi water-soluble. The arsenic trioxide dust is stored in 15 stope or rock chambers that have been sealed with concrete approximately 250 feet (76 meters) below the surface. The taxpayer-funded (c. $ 900m to approximately one billion dollars) remediation plan to permanently freeze the underground arsenic trioxide dust chambers was approved by the Canadian federal government in August 2014. According to

1425-468: Is rapidly increasing with population growth, while climate change is imposing additional stress on water resources and raising the probability of severe drought occurrence. The anthropogenic effects on groundwater resources are mainly due to groundwater pumping and the indirect effects of irrigation and land use changes. Groundwater plays a central role in sustaining water supplies and livelihoods in sub-Saharan Africa . In some cases, groundwater

1500-560: Is susceptible to saltwater intrusion in coastal areas and can cause land subsidence when extracted unsustainably, leading to sinking cities (like Bangkok ) and loss in elevation (such as the multiple meters lost in the Central Valley of California ). These issues are made more complicated by sea level rise and other effects of climate change , particularly those on the water cycle . Earth's axial tilt has shifted 31 inches because of human groundwater pumping. Groundwater

1575-400: Is the most accessed source of freshwater around the world, including as drinking water , irrigation , and manufacturing . Groundwater accounts for about half of the world's drinking water, 40% of its irrigation water, and a third of water for industrial purposes. Another estimate stated that globally groundwater accounts for about one third of all water withdrawals , and surface water for

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1650-491: Is the safe long-term storage 237,000 t (233,000 long tons; 261,000 short tons) of the arsenic trioxide dust, the lethal byproduct of extracting gold from the mineral arsenopyrite ore stored underground. Their top priority for the Giant Mine site remediation is an "effective, long-term management" of arsenic trioxide. Arsenic trioxide dust, which contains approximately 60% arsenic, is highly lethal even in small doses. It

1725-456: Is used for irrigation. Occasionally, sedimentary or "fossil" aquifers are used to provide irrigation and drinking water to urban areas. In Libya, for example, Muammar Gaddafi's Great Manmade River 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,

1800-748: The Department of Indian Affairs and Northern Development (DIAND) took over responsibility for cleaning up the Giant mine site. Miramar Mining Corporation subsequently entered into an arrangement with the government whereby Miramar held the mine operation in care and maintenance, continued underground dewatering operations, and removed the remaining ore from underground for treatment at the nearby Con Mine process facility (1999–2004). According to an article published in The Star in 2006, there were 15 sealed underground storage chambers 250 feet below ground containing

1875-535: The People's Bank of China has previously used troy measurements in minting Gold Pandas beginning in 1982; since 2016, the use of troy ounces has been replaced by integer numbers of grams. The troy pound (lb t) consists of twelve troy ounces and thus is 5 760 grains ( 373.241 72 grams). (An avoirdupois pound is approximately 21.53% heavier at 7 000 grains ( 453.592 37 grams), and consists of sixteen avoirdupois ounces). A troy ounce weighs 480 grains . Since

1950-585: The Punjab region of India , 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 groundwater-related subsidence and saltwater intrusion . 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

2025-545: The Yellowknives Dene First Nation (YKDFN) demonstrated outside the site demanding a federal apology, compensation, and a role in the contracts for remediation. They launched their own website which details the story from their point of view. The events and aftermath of the Giant Mine labour dispute and explosion were dramatized in the 1996 CBC television movie Giant Mine . Additionally,

2100-423: The grain , the pennyweight (24 grains), the troy ounce (20 pennyweights), and the troy pound (12 troy ounces). The troy grain is equal to the grain unit of the avoirdupois system, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. Legally, one troy ounce (oz t) equals exactly 31.1034768 grams. Troy weight is generally supposed to take its name from

2175-442: 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,

2250-554: The statutes of uncertain date from the reign of either Henry III or Edward I , thus before 1307, specifies " troni ponderacionem "—which the Public Record Commissioners translate as "troy weight". The word troni refers to markets. Wright's The English Dialect Dictionary lists the word troi as meaning a balance , related to the alternate form 'tron' which also means market or the place of weighing. From this, Watson suggests that 'troy' derives from

2325-405: The vadose zone below plant roots and is often expressed as a flux to the water table surface. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally (through the water cycle ) and through anthropogenic processes (i.e., "artificial groundwater recharge"), where rainwater and/or reclaimed water is routed to

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2400-521: The 12-ounce troy pound in the 19th century. It has been retained, though rarely used, in the American system. Larger amounts of precious metals are conventionally counted in hundreds or thousands of troy ounces, or in kilograms. Troy ounces have been and are still often used in precious metal markets in countries that otherwise use International System of Units (SI), except in East Asia . However,

2475-588: The French market town of Troyes where English merchants traded at least as early as the early 9th century. The name troy is first attested in 1390, describing the weight of a platter, in an account of the travels in Europe of the Earl of Derby . Charles Moore Watson (1844–1916) proposes an alternative etymology: The Assize of Weights and Measures (also known as Tractatus de Ponderibus et Mensuris ), one of

2550-579: The Northwest Territories to sort out. The site's 950 ha (2,300 acres) footprint includes 8 open pits , 4 tailing ponds , 325,000 m (11,500,000 cu ft) of contaminated soils , and approximately 100 buildings including a roaster/bag house complex that is highly contaminated with arsenic trioxide dust and fibrous asbestos . The remediation plan proposed by the SRK Consulting Inc. and SENES Consultants Limited,

2625-561: 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

2700-405: 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

2775-525: The aquifers are likely to run dry in 60 to 100 years. Groundwater provides critical freshwater 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 sustaining global ecology and meeting societal needs of drinking water and food production. The demand for groundwater

2850-598: 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. 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 km . 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

2925-510: 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, combined with increasing levels of salt in surface waters. As a consequence, major damage has occurred to local economies and environments. Aquifers in surface irrigated areas in semi-arid zones with reuse of

3000-474: The contamination is the topic of the interactive documentary "Shadow of a Giant" by Saskatchewan filmmaker Clark Ferguson who was artist in residence with Western Arctic Moving Pictures (WAMP) in 2013. Troy ounce Troy weight is a system of units of mass that originated in the Kingdom of England in the 15th century and is primarily used in the precious metals industry. The troy weight units are

3075-566: The continent. The troy ounce and grain were also part of the apothecaries' system . This was long used in medicine, but has been largely replaced by the metric system (milligrams). The only troy weight in widespread use is the British Imperial troy ounce and its American counterpart. Both are based on a grain of 0.06479891 gram (exact, by definition), with 480 grains to a troy ounce (compared with 437 + 1 ⁄ 2 grains for an ounce avoirdupois). The British Empire abolished

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3150-491: The current population growth rate. 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 drylands ". The Asia-Pacific region 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

3225-566: The explosion ( Fullowka v. Royal Oak Ventures Inc. ) In 2008, the nine Giant Mine widows lost their $ 10-million civil judgment when the Northwest Territories Supreme Court overturned an earlier ruling.. Roger Warren died in 2019. Mining operations over five decades have created a massive environmental liability, a problem which the mine's previous owners left to the Government of Canada and Government of

3300-404: The extended period over which the damage occurs. 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

3375-407: The extent, depth and thickness of water-bearing sediments and rocks. Before an investment is made in production wells, test wells may be 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. The characteristics of aquifers vary with

3450-400: The federal civil servant in charge of the clean-up, Jane Amphlett, using technology like that used in ice-hockey rinks, coolants will permanently freeze the storage chambers containing the arsenic trioxide dust to keep groundwater seepage out in what is called the "Frozen Block Method." A Yellowknife community museum is envisioned for part of the former Giant Mine townsite. In winter 2020

3525-506: The form of British pre-decimal pennies, in which pounds, shillings, and pence were indicated using the symbols £ , s , and d , respectively. There is no specific 'troy grain'. All Imperial systems use the same measure of mass called a grain (historically of barley ), each weighing 1 ⁄ 7000 of an avoirdupois pound (and thus a little under 65 milligrams). Mint masses, also known as moneyers' masses , were legalized by Act of Parliament dated 17 July 1649 entitled An Act touching

3600-472: 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

3675-404: The globe includes canals redirecting surface water, groundwater pumping, and diverting water from dams. Aquifers are critically 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. In India, 65% of the irrigation is from groundwater and about 90% of extracted groundwater

3750-416: 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 percolates into the aquifer through overlying unsaturated materials. 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

3825-475: The implementation of the international yard and pound agreement of 1 July 1959, the grain measure is defined as precisely 64.798 91   milligrams . Thus one troy ounce = 480 grains × 0.064 798 91 grams/grain = 31.103 476 80 grams. Since the ounce avoirdupois is defined as 437.5 grains, a troy ounce is exactly 480 ⁄ 437.5 = 192 ⁄ 175 or about 1.09714 ounces avoirdupois or about 9.7% more. The troy ounce for trading precious metals

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3900-699: The largest source of usable water storage in the United States , 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 Great Lakes . Many municipal water supplies are derived solely from groundwater. Over 2 billion people rely on it as their primary water source worldwide. Human use of groundwater causes environmental problems. For example, polluted groundwater

3975-487: The leading technical advisors since 2000 to Aboriginal Affairs and Northern Development Canada on the Giant Mine Remediation Project, includes underground issues such as dust that contains arsenic trioxide, and remediation of the surface, water and Baker Creek. Aboriginal Affairs and Northern Development Canada reported that the "greatest challenge associated with the remediation of Giant Mine"

4050-518: The local hydrogeology , may draw in non-potable water or 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. 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,

4125-466: The manner of weighing by balance precious goods such as bullion or drugs; in contrast to the word 'avoirdupois' used to describe bulk goods such as corn or coal, sometimes weighed in ancient times by a kind of steelyard called the auncel . Troy weight referred to the Tower system ; the earliest reference to the modern troy weights is in 1414. The origin of the troy weight system is unknown. Although

4200-487: The monies and coins of England . A grain is 20 mites, a mite is 24 droits, a droit is 20 perits, a perit is 24 blanks. The troy system was used in the apothecaries' system but with different further subdivisions. Groundwater This is an accepted version of this page Groundwater is the water present beneath Earth 's surface in rock and soil pore spaces and in the fractures of rock formations . About 30 percent of all readily available fresh water in

4275-412: The most productive sources of groundwater. Fluid flows can be altered in different lithological settings by brittle deformation of rocks in fault zones ; the mechanisms by which this occurs are the subject of fault zone hydrogeology . Reliance on groundwater will only increase, mainly due to growing water demand by all sectors combined with increasing variation in rainfall patterns . Groundwater

4350-623: The name probably comes from the Champagne fairs at Troyes , in northeastern France. English troy weights were nearly identical to the troy weight system of Bremen . (The Bremen troy ounce had a mass of 480.8 British Imperial grains.) Many aspects of the troy weight system were indirectly derived from the Roman monetary system . Before they used coins, early Romans used bronze bars of varying weights as currency. An aes grave ("heavy bronze") weighed one pound . One twelfth of an aes grave

4425-490: The old troy pound, there would have been 240 pennyweights to the pound (mass) – just as there were 240 pennies in the original pound-sterling . However, prior to 1526, the English pound sterling was based on the tower pound , which is 15 ⁄ 16 of a troy pound. The d in dwt stands for denarius , the ancient Roman coin that equates loosely to a penny. The symbol d for penny can be recognized in

4500-671: 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

4575-470: 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. 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." Global freshwater withdrawal

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4650-683: 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 2021 study found that of ~39 million investigated groundwater wells 6-20% are at high risk of running dry 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. Fresh-water aquifers, especially those with limited recharge by snow or rain, also known as meteoric water , can be over-exploited and depending on

4725-423: The roasting process. Arsenic trioxide readily dissolves in water; in 2006 underground flooding around Giant Mine's Mill Pond's underground chamber which contained 16,946 tonnes (16,678 long tons; 18,680 short tons) of arsenic trioxide dust threatened to migrate out of the chamber if it was flooded and dump large amounts of arsenic into Yellowknife Bay. On September 18, 1992, at the height of a labour dispute during

4800-423: The same terms as surface water : inputs, outputs and storage. The natural input to groundwater is seepage from surface water. The natural outputs from groundwater are springs 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

4875-416: 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. Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer . This process usually occurs in

4950-497: The subsurface. 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

5025-416: The tenure of Royal Oak Mines ownership, an explosion in a drift of the mine , 750 ft (230 m) underground, killed nine strikebreakers . Mine employee Roger Warren was later convicted of placing the bomb. The strike / lockout ended in 1993, pursuant to an order by the (then) Canada Labour Relations Board. A civil suit also resulted on behalf of the families of the replacement workers killed in

5100-408: 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 10,000 m /ha or more so the annual import of salt is in the order of 5,000 kg/ha or more. Under

5175-441: The world is groundwater. 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 the water table . Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps , and can form oases or wetlands . Groundwater

5250-519: 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. 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 . 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

5325-420: The world's total groundwater withdrawal. 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 arsenic , fluoride and salinity can reduce the suitability of groundwater as a drinking water source. Arsenic and fluoride have been considered as priority contaminants at

5400-587: Was based on, and virtually identical with, the pre-1824 British troy ounce and the pre-1707 English troy ounce. (1824 was the year the British Imperial system of weights and measures was adopted; 1707 was the year of the Act of Union which created the Kingdom of Great Britain .) Troy ounces have been used in England since the early 15th century, and the English troy ounce was officially adopted for coinage in 1527. Before that time, various sorts of troy ounces were in use on

5475-479: Was called an uncia , or in English, an "ounce". Before the adoption of the metric system, many systems of troy weights were in use in various parts of Europe, among them Holland troy, Paris troy, etc. Their values varied from one another by up to several percentage points. Troy weights were first used in England in the 15th century and were made official for gold and silver in 1527. The British Imperial system of weights and measures (also known as Imperial units )

5550-405: Was established in 1824, prior to which the troy weight system was a subset of pre-Imperial English units . The troy ounce in modern use is essentially the same as the British Imperial troy ounce (1824–1971), adopted as an official weight standard for United States coinage by act of Congress on May 19, 1828. The British Imperial troy ounce (known more commonly simply as the imperial troy ounce)

5625-402: 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 groundwater development, particularly for irrigation. The rate of increase is (as per 2022) approximately 1% per year, in tune with

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