Water well

Water well

Overview
A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 in underground aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

s. The well water is drawn by an electric submersible pump
Submersible pump
A submersible pump is a device which has a hermetically sealed motor close-coupled to the pump body. The whole assembly is submerged in the fluid to be pumped. The main advantage of this type of pump is that it prevents pump cavitation, a problem associated with a high elevation difference between...

, a trash pump, a vertical turbine pump, a handpump or a mechanical pump
Windmill
A windmill is a machine which converts the energy of wind into rotational energy by means of vanes called sails or blades. Originally windmills were developed for milling grain for food production. In the course of history the windmill was adapted to many other industrial uses. An important...

 (e.g. from a water-pumping windmill). It can also be drawn up using containers, such as buckets, that are raised mechanically or by hand.

Wells can vary greatly in depth, water volume and water quality.
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Encyclopedia
A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 in underground aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

s. The well water is drawn by an electric submersible pump
Submersible pump
A submersible pump is a device which has a hermetically sealed motor close-coupled to the pump body. The whole assembly is submerged in the fluid to be pumped. The main advantage of this type of pump is that it prevents pump cavitation, a problem associated with a high elevation difference between...

, a trash pump, a vertical turbine pump, a handpump or a mechanical pump
Windmill
A windmill is a machine which converts the energy of wind into rotational energy by means of vanes called sails or blades. Originally windmills were developed for milling grain for food production. In the course of history the windmill was adapted to many other industrial uses. An important...

 (e.g. from a water-pumping windmill). It can also be drawn up using containers, such as buckets, that are raised mechanically or by hand.

Wells can vary greatly in depth, water volume and water quality. Well water typically contains more minerals in solution than surface water and may require treatment to soften the water
Water softening
Water softening is the reduction of the concentration of calcium, magnesium, and certain other metal cations in hard water. These "hardness ions" can cause a variety of undesired effects including interfering with the action of soaps, the build up of limescale, which can foul plumbing, and...

 by removing minerals such as arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

, iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

.

Dug wells


Until recent centuries, all artificial wells were pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

less hand-dug wells of varying degrees of formality, and they remain a very important source of potable water in some rural developing areas where they are routinely dug and used today. Their indispensability has produced a number of literary references, literal and figurative, to them, including the Christian
Christianity
Christianity is a monotheistic religion based on the life and teachings of Jesus as presented in canonical gospels and other New Testament writings...

 Bible
Bible
The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

 story of Jesus
Jesus
Jesus of Nazareth , commonly referred to as Jesus Christ or simply as Jesus or Christ, is the central figure of Christianity...

 meeting a woman at Jacob
Jacob
Jacob "heel" or "leg-puller"), also later known as Israel , as described in the Hebrew Bible, the Talmud, the New Testament and the Qur'an was the third patriarch of the Hebrew people with whom God made a covenant, and ancestor of the tribes of Israel, which were named after his descendants.In the...

's well (John
Gospel of John
The Gospel According to John , commonly referred to as the Gospel of John or simply John, and often referred to in New Testament scholarship as the Fourth Gospel, is an account of the public ministry of Jesus...

 4:6) and the "Ding Dong Bell
Ding Dong Bell
"Ding Dong Bell" or "Ding Dong Dell" is a popular English language nursery rhyme. It has a Roud Folk Song Index number of 12853.-Lyrics:...

" nursery rhyme
Nursery rhyme
The term nursery rhyme is used for "traditional" poems for young children in Britain and many other countries, but usage only dates from the 19th century and in North America the older ‘Mother Goose Rhymes’ is still often used.-Lullabies:...

 about a cat in a well.

Hand-dug wells are excavations with diameters large enough to accommodate one or more men with shovels digging down to below the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...

. They can be lined with laid stones or brick; extending this lining upwards above the ground surface into a wall around the well serves to reduce both contamination and injuries by falling into the well. A more modern method called caissoning uses reinforced concrete or plain concrete pre-cast well rings that are lowered into the hole. A well-digging team digs under a cutting ring and the well column slowly sinks into the aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

, whilst protecting the team from collapse of the well bore.

Hand dug wells provide a cheap and low-tech solution to accessing groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 in rural locations in developing countries, and may be built with a high degree of community participation, or by local entrepreneurs who specialize in hand-dug wells. Hand dug wells have been successfully excavated to 60 metres (196.9 ft). Hand dug wells are inexpensive and low tech (compared to drilling) as they use mostly hand labour for construction. Hand dug wells have low operational and maintenance costs, in part because water can be extracted by hand bailing, without a pump. Hand dug wells can be easily deepened, which may be necessary if the ground water level drops, by telescoping the lining further down into the aquifer. The yield of existing hand dug wells may be improved by deepening or introducing vertical tunnels or perforated pipes.

Drawbacks to hand-dug wells are numerous. It can be impractical to hand dig wells in areas where hard rock is present, and they can be time-consuming to dig and line even in favorable areas. Because they exploit shallow aquifers, the well may be susceptible to yield fluctuations and possible contamination from surface water, including sewage. Hand dug well construction generally requires the use of a trained well construction team, and the capital investment for equipment such as concrete ring moulds, heavy lifting equipment, well shaft formwork, motorized de-watering pumps, and fuel can be large for people in developing countries. Construction of hand dug wells can be dangerous due to collapse of the well bore, falling objects and asphyxiation, including from dewatering pump exhaust fumes.

Woodingdean
Woodingdean
Woodingdean is an eastern suburb of the city of Brighton and Hove, East Sussex, separated from the main part of the city by downland and the Brighton Racecourse.-Source of name:...

 well, hand-dug between 1858 and 1862, is claimed to be the world's deepest hand-dug well at 1285 feet (391.7 m). The Big Well in Greensburg, Kansas
Greensburg, Kansas
Greensburg is a city in and the county seat of Kiowa County, Kansas, United States. As of the 2010 census, the city population was 777. Greensburg is also home to the world's largest hand-dug well....

 is billed as the world's largest hand-dug well, at 109 feet (33.2 m) deep and 32 feet (9.8 m) in diameter. However, the Well of Joseph in the Cairo Citadel
Cairo Citadel
The Saladin Citadel of Cairo is a medieval Islamic fortification in Cairo, Egypt. The location, on Mokattam hill near the center of Cairo, was once famous for its fresh breeze and grand views of the city...

 at 280 feet (85.3 m) deep and the Pozzo di S. Patrizio
Pozzo di S. Patrizio
The Pozzo di San Patrizio is a historical structure in Orvieto, Umbria, central Italy. It was built by Antonio da Sangallo of Orvieto, between 1527 and 1537, at the behest of Pope Clement VII....

 (St. Patrick's Well) built in 1527 in Orvieto, Italy
Orvieto
Orvieto is a city and comune in Province of Terni, southwestern Umbria, Italy situated on the flat summit of a large butte of volcanic tuff...

, at 61 metres (200.1 ft) deep by 13 metres (42.7 ft) wide are both larger by volume.

Driven wells


Driven wells may be very simply created in unconsolidated material with a "well point", which consists of a hardened drive point and a screen (perforated pipe). The point is simply hammered into the ground, usually with a tripod and "driver", with pipe sections added as needed. A driver is a weighted pipe that slides over the pipe being driven and is repeatedly dropped on it. When groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 is encountered, the well is washed of sediment and a pump installed.

Drilled wells


.

Drilled wells are typically created using either top-head rotary style, table rotary, or cable tool drilling machines, all of which use drilling stems that are turned to create a cutting action in the

Drilled wells can be excavated by simple hand drilling methods (augering, sludging, jetting, driving, hand percussion) or machine drilling (rotary, percussion, down the hole hammer). Drilled wells can get water from a much deeper level than can dug wells - often up to several hundred metres.

Drilled wells with electric pumps are currently used throughout the world, typically in rural or sparsely populated areas, though many urban areas are supplied partly by municipal wells formation, hence the term 'drilling'. Most shallow well drilling machines are mounted on large trucks, trailers, or tracked vehicle carriages. Water wells typically range from 3 to 18 m deep, but in some areas can go deeper than 900 m.

Rotary drilling machines use a segmented steel drilling string, typically made up of 6 m sections of galvanized steel tubing that are threaded together, with a bit or other drilling device at the bottom end. Some rotary drilling machines are designed to in conjunction with the drilling of the actual bore hole. Air and/or water is used as a circulation fluid to displace cuttings and cool bits during the drilling. Another form of rotary style drilling, termed 'mud rotary', makes use of a specially made mud, or drilling fluid, which is constantly being altered during the drill so that it can consistently create enough hydraulic pressure to hold the side walls of the bore hole open, regardless of the presence of a casing in the well. Typically, boreholes drilled into solid rock are not cased until after the drilling process is completed, regardless of the machinery used.

The oldest form of drilling machinery is the Cable Tool, still used today. Specifically designed to raise and lower a bit into the bore hole, the 'spudding' of the drill causes the bit to be raised and dropped onto the bottom of the hole, and the design of the cable causes the bit to twist at approximately ¼ revolution per drop, thereby creating a drilling action. Unlike rotary drilling, cable tool drilling requires the drilling action to be stopped so that the bore hole can be bailed or emptied of drilled cuttings.

Drilled wells are usually cased with a factory-made pipe, typically steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 (in air rotary or cable tool drilling) or plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

/PVC
PVC
Polyvinyl chloride is a plastic.PVC may also refer to:*Param Vir Chakra, India's highest military honor*Peripheral venous catheter, a small, flexible tube placed into a peripheral vein in order to administer medication or fluids...

 (in mud rotary wells, also present in wells drilled into solid rock). The casing is constructed by welding, either chemically or thermodynamically, segments of casing together. If the casing is installed during the drilling, most drills will drive the casing into the ground as the bore hole advances, while some newer machines will actually allow for the casing to be rotated and drilled into the formation in a similar manner as the bit advancing just below. PVC or plastic is typically welded and then lowered into the drilled well, vertically stacked with their ends nested and either glued or splined together. The sections of casing are usually 6 m or more in length, and 6 to 12 in (15.2 to 30.5 cm) in diameter, depending on the intended use of the well and local groundwater conditions.

Surface contamination of wells in the United States is typically controlled by the use of a 'surface seal'. A large hole is drilled to a predetermined depth or to a confining formation (clay or bedrock, for example), and then a smaller hole for the well is completed from that point forward. The well is typically cased from the surface down into the smaller hole with a casing that is the same diameter as that hole. The annular space between the large bore hole and the smaller casing is filled with bentonite clay, concrete, or other sealant material. This creates an impermeable seal from the surface to the next confining layer that keeps contaminants from traveling down the outer sidewalls of the casing or borehole and into the aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

. In addition, wells are typically capped with either an engineered well cap or seal that vents air through a screen into the well, but keeps insects, small animals, and unauthorized persons from accessing the well.

At the bottom of wells, based on formation, a screening device, filter pack, slotted casing, or open bore hole is left to allow the flow of water into the well. Constructed screens are typically used in unconsolidated formations (sands, gravels, etc.), allowing water and a percentage of the formation to pass through the screen. Allowing some material to pass through creates a large area filter out of the rest of the formation, as the amount of material present to pass into the well slowly decreases and is removed from the well. Rock wells are typically cased with a PVC liner/casing and screen or slotted casing at the bottom, this is mostly present just to keep rocks from entering the pump assembly. Some wells utilize a 'filter pack' method, where an undersized screen or slotted casing is placed inside the well and a filter medium is packed around the screen, between the screen and the borehole or casing. This allows the water to be filtered of unwanted materials before entering the well and pumping zone.

Classification



There are two broad classes of drilled-well types, based on the type of aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

 the well is in:
  • Shallow or unconfined wells are completed in the uppermost saturated aquifer at that location (the upper unconfined aquifer).
  • Deep or confined wells are sunk through an impermeable stratum into an aquifer that is sandwiched between two impermeable strata (aquitards or aquicludes). The majority of deep aquifers are classified as artesian because the hydraulic head in a confined well is higher than the level of the top of the aquifer. If the hydraulic head in a confined well is higher than the land surface it is a "flowing" artesian well (named after Artois
    Artois
    Artois is a former province of northern France. Its territory has an area of around 4000 km² and a population of about one million. Its principal cities are Arras , Saint-Omer, Lens and Béthune.-Location:...

     in France
    France
    The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

    ).


Two additional broad classes of well types may be distinguished, based on the use of the well:
  • production or pumping wells, are large diameter (greater than 15 cm in diameter) cased (metal, plastic, or concrete) water wells, constructed for extracting water from the aquifer by a pump
    Pump
    A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

     (if the well is not artesian
    Artesian aquifer
    An artesian aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached. This type of well is called an artesian well...

    ).
  • monitoring wells or piezometer
    Piezometer
    A piezometer is either a device used to measure static liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity, or a device which measures the pressure of groundwater at a specific point...

    s
    , are often smaller diameter wells used to monitor the hydraulic head or sample the groundwater for chemical constituents. Piezometers are monitoring wells completed over a very short section of aquifer. Monitoring wells can also be completed at multiple levels, allowing discrete samples or measurements to be made at different vertical elevations at the same map location.


Obviously, a well constructed for pumping groundwater can be used passively as a monitoring well and a small diameter well can be pumped, but this distinction by use is common.

Siting


Before excavation, information about the geology, water table depth, seasonal fluctuations, recharge area and rate must be found. This work is typically done by a hydrogeologist, or a groundwater surveyor using a variety of tools including electro-seismic surveying, any available information from nearby wells, geologic maps sometimes geophysical imaging
Geophysical imaging
Geophysical imaging is geophysical technique that investigates the subsurface. There are many different kinds of imaging techniques, all which are based on applied physics.Types of geophysical imaging include:...

.

Contamination



Shallow pumping wells can often supply drinking water
Drinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...

 at a very low cost, but because impurities from the surface easily reach shallow sources, a greater risk of contamination occurs for these wells when they are compared to deeper wells. Dug and driven wells are relatively easy to contaminate, and dug wells are unreliable in most of the U.S.

The quality of the well water can be significantly increased by lining the well, sealing the well head, fitting a self-priming hand pump, constructing an apron, ensuring the area is kept clean and free from stagnant water and animals, moving sources of contamination (latrines, garbage pits) and carrying out hygiene education. The well should be cleaned with 1% chlorine solution after construction and periodically every 6 months.

Microorganisms


Most of the bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, viruses, parasites, and fungi that contaminate well water comes from fecal material
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

 from humans and other animals. Common bacterial contaminants include E. coli, Salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...

, Shigella
Shigella
Shigella is a genus of Gram-negative, nonspore forming, non-motile, rod-shaped bacteria closely related to Escherichia coli and Salmonella. The causative agent of human shigellosis, Shigella causes disease in primates, but not in other mammals. It is only naturally found in humans and apes. During...

, and Campylobacter jejuni
Campylobacter jejuni
Campylobacter jejuni is a species of curved, helical-shaped, non-spore forming, Gram-negative, microaerophilic bacteria commonly found in animal feces. It is one of the most common causes of human gastroenteritis in the world. Food poisoning caused by Campylobacter species can be severely...

. Common viral contaminants include norovirus, sapovirus
Sapovirus
Sapoviruses are caliciviruses that together with the noroviruses, are the most common cause of acute viral gastroenteritis in adults. The type species is Sapporo virus...

, rotavirus
Rotavirus
Rotavirus is the most common cause of severe diarrhoea among infants and young children, and is one of several viruses that cause infections often called stomach flu, despite having no relation to influenza. It is a genus of double-stranded RNA virus in the family Reoviridae. By the age of five,...

, enterovirus
Enterovirus
Enteroviruses are a genus of ssRNA viruses associated with several human and mammalian diseases. Serologic studies have distinguished 66 human enterovirus serotypes on the basis of antibody neutralization tests. Additional antigenic variants have been defined within several of the serotypes on the...

es, and hepatitis A
Hepatitis A
Hepatitis A is an acute infectious disease of the liver caused by the hepatitis A virus , an RNA virus, usually spread the fecal-oral route; transmitted person-to-person by ingestion of contaminated food or water or through direct contact with an infectious person...

 and E
Hepatitis E
Hepatitis E is a viral hepatitis caused by infection with a virus called hepatitis E virus . HEV is a positive-sense single-stranded RNA icosahedral virus with a 7.5 kilobase genome. HEV has a fecal-oral transmission route. It is one of five known hepatitis viruses: A, B, C, D, and E...

. Parasites include Giardia lamblia
Giardia lamblia
Giardia lamblia is a flagellated protozoan parasite that colonizes and reproduces in the small intestine, causing giardiasis. The giardia parasite attaches to the epithelium by a ventral adhesive disc, and reproduces via binary fission...

, Cryptosporidium
Cryptosporidium
Cryptosporidium is a protozoan that can cause gastro-intestinal illness with diarrhea in humans.Cryptosporidium is the organism most commonly isolated in HIV positive patients presenting with diarrhea...

, Cyclospora cayetanensis
Cyclospora cayetanensis
Cyclospora cayetanensis is a protozoan that causes disease in humans, and perhaps other primates. It has been linked in the United States from fecally-contaminated imported raspberries and was virtually unknown before about 1990, but has been on the rise since...

, and microsporidia
Microsporidia
The microsporidia constitute a phylum of spore-forming unicellular parasites. They were once thought to be protists but are now known to be fungi. Loosely 1500 of the probably more than one million species are named now. Microsporidia are restricted to animal hosts, and all major groups of animals...

.

Chemicals


Chemical contamination is a common problem with groundwater. Nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

s from sewage
Sewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...

 or fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

 are a particular problem for children. Pollutant chemicals include pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s and volatile organic compound
Volatile organic compound
Volatile organic compounds are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and...

s from gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

, dry-cleaning, the fuel additive methyl tert-butyl ether
Methyl tert-butyl ether
Methyl tert-butyl ether, also known as methyl tertiary butyl ether and MTBE, is an organic compound with molecular formula 3COCH3. MTBE is a volatile, flammable, and colorless liquid that is immiscible with water. It has a minty odor vaguely reminiscent of diethyl ether, leading to unpleasant taste...

 (MTBE), and perchlorate
Perchlorate
Perchlorates are the salts derived from perchloric acid . They occur both naturally and through manufacturing. They have been used as a medicine for more than 50 years to treat thyroid gland disorders. They are used extensively within the pyrotechnics industry, and ammonium perchlorate is also a...

 from rocket fuel, airbag inflators, and other artificial and natural sources.

Several minerals are also contaminants, including lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 leached from brass fittings or old lead pipes, chromium VI from electroplating and other sources, naturally occurring arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

, radon
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...

, and uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

—all of which can cause cancer—and naturally occurring fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...

, which is desirable in low quantities to prevent tooth decay, but can cause dental fluorosis
Dental fluorosis
Dental fluorosis is a developmental disturbance of dental enamel caused by excessive exposure to high concentrations of fluoride during tooth development. The risk of fluoride overexposure occurs between the ages of 3 months and 8 years. In its mild forms , fluorosis often appears as unnoticeable,...

 in higher concentrations.

Some chemicals are commonly present in water wells at levels that are not toxic, but can cause other problems. Calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 and magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 cause what is known as hard water
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...

, which can precipitate and clog pipes or burn out water heaters. Iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

 can appear as dark flecks that stain clothing and plumbing, and can promote the growth of iron and manganese bacteria
Iron bacteria
In the management of water-supply wells, iron bacteria are bacteria that derive the energy they need to live and multiply by oxidizing dissolved ferrous iron . The resulting ferric oxide is insoluble, and appears as brown gelatinous slime that will stain plumbing fixtures, and clothing or utensils...

 that can form slimy black colonies that clog pipes.

Mitigation


Cleanup of contaminated groundwater tends to be very costly. Effective remediation of groundwater is generally very difficult.

Contamination of groundwater from surface and subsurface sources can usually be dramatically reduced by correctly centering the casing during construction and filling the casing annulus with an appropriate sealing material. The sealing material (grout) should be placed from immediately above the production zone back to surface, because, in the absence of a correctly constructed casing seal, contaminated fluid can travel into the well through the casing annulus. Centering devices are important (usually 1 per length of casing or at maximum intervals of 9 m) to ensure that the grouted annular space is of even thickness.
Upon the construction of a new test well, it is considered best practice to invest in a complete battery of chemical and biological tests on the well water in question. Point-of-use treatment is available for individual properties and treatment plants are often constructed for municipal water supplies that suffer from contamination. Most of these treatment methods involve the filtration
Filtration
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...

 of the contaminants of concern, and additional protection may be garnered by installing well-casing screens only at depths where contamination is not present.

Well water for personal use is often filtered with reverse osmosis
Reverse osmosis
Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...

 water processors; this process can remove very small particles. A simple, effective way of killing microorganisms is to bring the water to a full boil for one to three minutes, depending on location. A household well contaminated by microorganisms can initially be treated by shock chlorination using bleach, generating concentrations hundreds of times greater than found in community water systems; however, this will not fix any structural problems that led to the contamination and generally requires some expertise and testing for effective application.

Environmental problems


A risk with the placement of water wells is soil salination. This problem occurs when the watertable of the soil begins to drop and salt begins to accumulate as the soil begins to dry out. Another environmental problem that is very prevalent in water well drilling is the potential for methane to seep through.

Soil salination


The potential for soil salination is a large risk when choosing the placement of water wells. Soil salination is caused when the water table of the soil drops over time and salt begins to accumulate. In turn, the increased amount of salt begins to dry the soil out. This is a very detrimental problem because the increased level of salt in the soil can result in the degradation of soil and can be very harmful to vegetation.

Methane


Methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, an asphyxiate, is a chemical compound that is the main component of natural gas. When methane mixes with oxygen, it has the ability to reduce oxygen to harmfully low levels in a small space or to form an explosion. This explosive quality is what poses such a danger in regards to the drilling and placement of water wells.

Low levels of methane in drinking water are not considered toxic. When methane seeps into a water supply, it is commonly referred to as "methane migration." This can be caused by old natural gas wells near water well systems becoming abandoned and no longer monitored.

Ancient well technologies




The earliest wells are known from the Neolithic
Neolithic
The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...

. In the submerged Pre-Pottery Neolithic B
Pre-Pottery Neolithic B
Pre-Pottery Neolithic B is a division of the Neolithic developed by Dame Kathleen Kenyon during her archaeological excavations at Jericho in the southern Levant region....

 settlement of Atlit Yam
Atlit Yam
Atlit Yam is an ancient submerged Neolithic village off the coast of Atlit, Israel.-History:Atlit-Yam provides the earliest known evidence for an agro-pastoral-marine subsistence system on the Levantine coast. The final Pre-Pottery Neolithic B site of Atlit Yam dates between 6900 and 6300 BC...

 in Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

, dated to 8100–7500 BC, a well has been found, which so far is the oldest known. Other PPNB wells (7–8 m deep) are known from Kissonerga-Mylouthkia on Cyprus
Cyprus
Cyprus , officially the Republic of Cyprus , is a Eurasian island country, member of the European Union, in the Eastern Mediterranean, east of Greece, south of Turkey, west of Syria and north of Egypt. It is the third largest island in the Mediterranean Sea.The earliest known human activity on the...

 and maybe shallower examples from Shillourokambos
Shillourokambos
Shillourokambos is an aceramic Neolithic site near Parekklisha, 6 km east of Limassol in southern Cyprus. It is located on a low plateau. Excavations began in 1992...

 as well.

Wood-lined wells are known from the early Neolithic Linear Pottery culture
Linear Pottery culture
The Linear Pottery culture is a major archaeological horizon of the European Neolithic, flourishing ca. 5500–4500 BC.It is abbreviated as LBK , is also known as the Linear Band Ware, Linear Ware, Linear Ceramics or Incised Ware culture, and falls within the Danubian I culture of V...

, for example in Kückhoven, dated 5090 BC and Eythra, dated 5200 BC in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 and Schletz in Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

. The early Mesolithic
Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....

 site of Friesack
Friesack
Friesack is a town in the Havelland district, in Brandenburg, Germany. It is situated northeast of Rathenow, and southwest of Neuruppin. It is known for its Mesolithic archaeological site.-Film shot in Friesack:...

 in Germany has yielded a shallow pit with the remains of a birch-bark
Birch bark
Birch bark or birchbark is the bark of several Eurasian and North American birch trees of the genus Betula.The strong and water-resistant cardboard-like bark can be easily cut, bent, and sewn, which made it a valuable building, crafting, and writing material, since pre-historic times...

 container that may have been a shallow artificial well.

Australian Aborigines
Australian Aborigines
Australian Aborigines , also called Aboriginal Australians, from the latin ab originem , are people who are indigenous to most of the Australian continentthat is, to mainland Australia and the island of Tasmania...

 relied on wells to survive the harsh Australian desert
Deserts of Australia
Deserts cover a large portion of the land in Australia. Most of the deserts lie in the central and north-western part of the country. The largest part of Australia is desert or semi-arid...

. They would dig down, scooping out sand and mud to reach clean water, then cover the source with spinifex
Triodia (plant genus)
Triodia is a large genus of hummock-forming grass endemic to Australia; they are commonly known as spinifex, although they are not a part of the coastal genus Spinifex. There are currently 64 recognised species...

 to prevent spoilage. Non-aborigines call these native wells, soaks or soakage
Soakage
A soakage, or soak, is a source of water in Australian deserts.It is called thus because the water generally seeps into the sand, and is stored below, sometimes as part of an ephemeral river or creek system.-Aboriginal water source:...

s.

Stepwell
Stepwell
Stepwells, also called bawdi or baoli , or vaav are wells or ponds in which the water can be reached by descending a set of steps. They may be covered and protected, and are often of architectural significance...

s are common in the west of India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

. In these wells, the water may be reached by descending a set of steps. They may be covered and are often of architectural significance. Many stepwells were also used for leisure, providing relief from the daytime heat.
A qanat
Qanat
A qanāt is a water management system used to provide a reliable supply of water for human settlements and irrigation in hot, arid and semi-arid climates...

 is an ancient water collection system made up of a series of wells and linked underground water channels that collects flowing water from a source usually a distance away, stores it, and then brings the water to the surface using gravity. Much of the population of Iran and other arid countries in Asia and North Africa historically depended upon the water from qanats; the areas of population corresponded closely to the areas where qanats are possible.

In Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

, shadoof
Shadoof
A shadoof, shaduf, dhenkli, picottah or counterpoise-lift is an irrigation tool...

s and sakiehs are used. When compared to each other however, the Sakkieh is much more efficient, as it can bring up water from a depth of 10 meters (versus the 3 meters of the shadoof). The Sakieh is the Egyptian version of the Noria
Noria
A noria is a machine for lifting water into a small aqueduct, either for the purpose of irrigation or, in at least one known instance, to feed seawater into a saltern....

.

From the Iron Age
Iron Age
The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...

 onwards, wells are common archaeological features, both with wooden shafts and shaft linings made from wickerwork.

Lately, however, the described wells/pumps are no longer very efficient and can be replaced by either handpumps or treadle pump
Treadle Pump
A treadle pump is a human-powered pump designed to lift water from a depth of seven metres or less. A treadle is a lever device pressed by the foot to drive a machine, in this case a pump. The treadle pump can do most of the work of a motorized pump, but costs considerably less to purchase...

s. Another alternative is the use of self-dug wells, electrical deep-well pumps (for higher depths). Appropriate technology
Appropriate technology
Appropriate technology is an ideological movement originally articulated as "intermediate technology" by the economist Dr...

 organizations as Practical Action
Practical Action
Practical Action is a development charity registered in the United Kingdom which works directly in four regions of the developing world – Latin America, East Africa, Southern Africa and South Asia, with particular concentration on Peru, Kenya, Sudan, Zimbabwe, Sri Lanka and Nepal.In these countries,...

 are now supplying information on how to build/set-up (diy) handpumps and treadle pump
Treadle Pump
A treadle pump is a human-powered pump designed to lift water from a depth of seven metres or less. A treadle is a lever device pressed by the foot to drive a machine, in this case a pump. The treadle pump can do most of the work of a motorized pump, but costs considerably less to purchase...

s in practice.

Cultural references




Springs and wells have had cultural significance since prehistoric times, leading to the foundation of towns such as Wells
Wells
Wells is a cathedral city and civil parish in the Mendip district of Somerset, England, on the southern edge of the Mendip Hills. Although the population recorded in the 2001 census is 10,406, it has had city status since 1205...

 and Bath in Somerset
Somerset
The ceremonial and non-metropolitan county of Somerset in South West England borders Bristol and Gloucestershire to the north, Wiltshire to the east, Dorset to the south-east, and Devon to the south-west. It is partly bounded to the north and west by the Bristol Channel and the estuary of the...

. Interest in health benefits led to the growth of spa town
Spa town
A spa town is a town situated around a mineral spa . Patrons resorted to spas to "take the waters" for their purported health benefits. The word comes from the Belgian town Spa. In continental Europe a spa was known as a ville d'eau...

s including many with wells in their name, examples being Llandrindod Wells
Llandrindod Wells
Llandrindod Wells , colloquially known locally as "Llandod", is a town and community in Powys, within the historic boundaries of Radnorshire, mid Wales, United Kingdom. It was developed as a spa town in the 19th century, with a boom in the late 20th century as a centre of local government. Before...

 and Royal Tunbridge Wells
Royal Tunbridge Wells
Royal Tunbridge Wells is a town in west Kent, England, about south-east of central London by road, by rail. The town is close to the border of the county of East Sussex...

.

Empty wells are a prominent element in some of the work of Japanese author Haruki Murakami
Haruki Murakami
is a Japanese writer and translator. His works of fiction and non-fiction have garnered him critical acclaim and numerous awards, including the Franz Kafka Prize and Jerusalem Prize among others.He is considered an important figure in postmodern literature...

, especially The Wind-Up Bird Chronicle
The Wind-Up Bird Chronicle
is a novel by Haruki Murakami. The first published translation was by Alfred Birnbaum. The American translation and its British adaptation, dubbed the "only official translations" are by Jay Rubin and were first published in 1997...

.

In Lewis Carroll
Lewis Carroll
Charles Lutwidge Dodgson , better known by the pseudonym Lewis Carroll , was an English author, mathematician, logician, Anglican deacon and photographer. His most famous writings are Alice's Adventures in Wonderland and its sequel Through the Looking-Glass, as well as the poems "The Hunting of the...

's Alice in Wonderland, chapter 7, The Dormouse tells the history of a family who lived "at the bottom of a well", made of treacle (see treacle mining
Treacle mining
Treacle mining is the fictitious mining of treacle in a raw form similar to coal. The subject purports to be serious but is an attempt to test credulity. Thick black treacle makes the deception plausible...

).

There is a belief that a wish can be made in a well; see wishing well
Wishing well
A wishing well is a term from European folklore to describe wells where it was thought that any spoken wish would be granted. The idea that a wish would be granted came from the idea that water housed deities or had been placed there as a gift from the gods, since water was a source of life and...

.
There is much folklore
Folklore
Folklore consists of legends, music, oral history, proverbs, jokes, popular beliefs, fairy tales and customs that are the traditions of a culture, subculture, or group. It is also the set of practices through which those expressive genres are shared. The study of folklore is sometimes called...

 in Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 surrounding wells, particularly in relation to their healing properties. In Scotland and Ireland, there is a Celt
Celt
The Celts were a diverse group of tribal societies in Iron Age and Roman-era Europe who spoke Celtic languages.The earliest archaeological culture commonly accepted as Celtic, or rather Proto-Celtic, was the central European Hallstatt culture , named for the rich grave finds in Hallstatt, Austria....

ic tradition of leaving cloth offerings
Offerings
Offerings may refer to:* Offerings , a slasher film* Offerings , the second album by VAS* Offerings: A Worship Album, a worship album by Christian band Third Day...

 for healing at Clootie well
Clootie well
Clootie wells are places of pilgrimage in Celtic areas. They are wells or springs, almost always with a tree growing beside them, where strips of cloth or rags have been left, usually tied to the branches of the tree as part of a healing ritual...

s. In the Peak District
Peak District
The Peak District is an upland area in central and northern England, lying mainly in northern Derbyshire, but also covering parts of Cheshire, Greater Manchester, Staffordshire, and South and West Yorkshire....

 of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, a tradition of Well dressing
Well dressing
Well dressing is a summer custom practised in rural England in which wells, springs or other water sources are decorated with designs created from flower petals...

 has persisted from Pagan to Christian
Christian
A Christian is a person who adheres to Christianity, an Abrahamic, monotheistic religion based on the life and teachings of Jesus of Nazareth as recorded in the Canonical gospels and the letters of the New Testament...

 religion, possibly related to plague.

Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...

 first calculated the radius of the Earth in about 230 BC by comparing shadows in wells during the summer solstice.

In Western Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...

, water wells were traditionally centers of social life, and the community came together to build them using a traditional process. Local stories often emphasize the social and cultural values of wells. The wells were decorated and had a wooden wheel attached to raise the bucket. Wells are still used in many Ukrainian towns and cities.

The same is true with the early Israelites, as depicted in the Hebrew Bible
Bible
The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

 and in the Christian
Christian
A Christian is a person who adheres to Christianity, an Abrahamic, monotheistic religion based on the life and teachings of Jesus of Nazareth as recorded in the Canonical gospels and the letters of the New Testament...

 New Testament
New Testament
The New Testament is the second major division of the Christian biblical canon, the first such division being the much longer Old Testament....

. Many Bible stories take place around wells, such as the finding of a wife for Isaac
Isaac
Isaac as described in the Hebrew Bible, was the only son Abraham had with his wife Sarah, and was the father of Jacob and Esau. Isaac was one of the three patriarchs of the Israelites...

 in Genesis and Jesus
Jesus
Jesus of Nazareth , commonly referred to as Jesus Christ or simply as Jesus or Christ, is the central figure of Christianity...

's talk with the Samaritan woman in the Gospels.

In the novel Ring
Ring (Suzuki novel)
is a Japanese horror novel by Koji Suzuki, first published in 1991, and set in modern day Japan. It was the basis for a film of the same name , and two remakes: a Korean version and an American version ....

 by Koji Suzuki, and subsequent film adaptations, the malevolent antagonist, Sadako Yamamura, is revealed to have been killed and thrown into a well some thirty years before the events of the novel. Sadako's well is a recurring theme in the story, especially in the 1998 film adaptation
Ring (film)
is a 1998 Japanese horror film by Hideo Nakata, adapted from the novel Ring by Kōji Suzuki, which in turn draws on the Japanese folk tale Banchō Sarayashiki. The film stars Nanako Matsushima, Hiroyuki Sanada, and Rikiya Ōtaka as members of a divorced family...

.

In an album called Märchen
Märchen (album)
Märchen is the seventh story CD, released by the fantasy symphonic rock band Sound Horizon on December 15, 2010 through King Records. The limited edition released few days before the normal edition. The normal edition debuted No.3 and peaked No.2 on the Oricon weekly album charts...

 by Japanese band Sound Horizon
Sound Horizon
Sound Horizon, abbreviated by fans as Sanhora , is a Japanese musical group with composer Revo as the leader. They call themselves the "fantasy band" and have released their works that closely resemble suites.-History:...

, a well plays an important part as a reference to id. Ido (イド), as written in the booklet, can be read as "well" or "id".

External links