Well

A well is an excavation or structure created in the ground by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The well water is drawn by a pump, or using containers, such as buckets, that are raised mechanically or by hand. Wells were first constructed at least eight thousand years ago and historically vary in construction from a simple scoop in the sediment of a dry watercourse to the qanats of Iran, and the stepwells and sakiehs of India. Placing a lining in the well shaft helps create stability, and linings of wood or wickerwork date back at least as far as the Iron Age.

Wells have traditionally been sunk by hand digging, as is the case in rural areas of the developing world. These wells are inexpensive and low-tech as they use mostly manual labour, and the structure can be lined with brick or stone as the excavation proceeds. A more modern method called caissoning uses pre-cast reinforced concrete well rings that are lowered into the hole. Driven wells can be created in unconsolidated material with a well hole structure, which consists of a hardened drive point and a screen of perforated pipe, after which a pump is installed to collect the water. Deeper wells can be excavated by hand drilling methods or machine drilling, using a bit in a borehole. Drilled wells are usually cased with a factory-made pipe composed of steel or plastic. Drilled wells can access water at much greater depths than dug wells.

Two broad classes of well are shallow or unconfined wells completed within the uppermost saturated aquifer at that location, and deep or confined wells, sunk through an impermeable stratum into an aquifer beneath. A collector well can be constructed adjacent to a freshwater lake or stream with water percolating through the intervening material. The site of a well can be selected by a hydrogeologist, or groundwater surveyor. Water may be pumped or hand drawn. Impurities from the surface can easily reach shallow sources and contamination of the supply by pathogens or chemical contaminants needs to be avoided. Well water typically contains more minerals in solution than surface water and may require treatment before being potable. Soil salination can occur as the water table falls and the surrounding soil begins to dry out. Another environmental problem is the potential for methane to seep into the water.

Faryab- village dug well
A dug well in a village in Faryab Province, Afghanistan.
Markowa stodoła
A dug well, large shadoof (well sweep), and old barn in Markowa, Poland

History

Tunis1960-150 hg
Camel drawing water from a well, Djerba island, Tunisia
Model well, burial find, China, Han dynasty, 206 BC to 220 AD, earthenware - Östasiatiska museet, Stockholm - DSC09578
A Chinese ceramic model of a well with a water pulley system, excavated from a tomb of the Han Dynasty (202 BC - 220 AD) period

Wood-lined wells are known from the early Neolithic Linear Pottery culture, for example in Kückhoven (an outlying centre of Erkelenz), dated 5090 BC and Eythra, dated 5200 BC in Schletz (an outlying centre of Asparn an der Zaya) in Austria.[1]

Some of the earliest evidence of water wells are located in China. The neolithic Chinese discovered and made extensive use of deep drilled groundwater for drinking. The Chinese text The Book of Changes, originally a divination text of the Western Zhou dynasty (1046 -771 BC), contains an entry describing how the ancient Chinese maintained their wells and protected their sources of water.[2] Archaeological evidence and old Chinese documents reveal that the prehistoric and ancient Chinese had the aptitude and skills for digging deep water wells for drinking water as early as 6000 to 7000 years ago. A well excavated at the Hemedu excavation site was believed to have been built during the neolithic era.[3] The well was cased by four rows of logs with a square frame attached to them at the top of the well. 60 additional tile wells southwest of Beijing are also believed to have been built around 600 BC for drinking and irrigation.[4][5]

In Egypt, shadoofs and sakiehs are used.[6][7] When compared to each other however, the Sakkieh is much more efficient, as it can bring up water from a depth of 10 metres (versus the 3 metres of the shadoof). The Sakieh is the Egyptian version of the Noria. Some of the world's oldest known wells, located in Cyprus, date to 7000-8500 BC.[8] Two wells from the Neolithic period, around 6500 BC, have been discovered in Israel. One is in Atlit, on the northern coast of Israel, and the other is the Jezreel Valley.[9]

Wells for other purposes came along much later, historically. The first recorded salt well was dug in the Sichuan province of China around 2,250 years ago. This was the first time that ancient water well technology was applied successfully for the exploitation of salt, and marked the beginning of Sichuan’s salt drilling industry.[10] The earliest known oil wells were also drilled in China, in 347 CE. These wells had depths of up to about 240 metres (790 ft) and were drilled using bits attached to bamboo poles.[11] The oil was burned to evaporate brine and produce salt. By the 10th century, extensive bamboo pipelines connected oil wells with salt springs. The ancient records of China and Japan are said to contain many allusions to the use of natural gas for lighting and heating. Petroleum was known as Burning water in Japan in the 7th century.[12]

Types

Uwaynat bin Hussain water well near Simaisma
Water well near Simaisma, eastern Qatar
Leather bucket of a well
Leather bucket used for the water well.
Well, Historical Village , Bhaini Sahib, Ludhyana , Punjab , India
Well, Historical Village, Bhaini Sahib, Ludhiana, Punjab, India

Dug wells

Well.handdug.cased.mali
View into a hand-dug well cased with concrete rings; Ouelessebougou, Mali.
Well In Kerala
A dug well in a village in Kerala, India.

Until recent centuries, all artificial wells were pumpless hand-dug wells of varying degrees of sophistication, 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 reference to the incident of Jesus meeting a woman at Jacob's well (John 4:6) in the bible and the "Ding Dong Bell" nursery rhyme about a cat in a well.

Hand-dug wells are excavations with diameters large enough to accommodate one or more people with shovels digging down to below the water table. The excavation is braced horizontally to avoid landslide or erosion endangering the people digging. They can be lined with laid stones or brick; extending this lining upwards above the ground surface to form 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, whilst protecting the team from collapse of the well bore.

Hand-dug wells are inexpensive and low tech (compared to drilling) as they use mostly manual labour to access groundwater in rural locations in developing countries. They may be built with a high degree of community participation, or by local entrepreneurs who specialize in hand-dug wells. They have been successfully excavated to 60 metres (200 ft). They have low operational and maintenance costs, in part because water can be extracted by hand bailing, without a pump. The water is often coming from an aquifer or groundwater, and 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 favourable 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 well trained 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 well, hand-dug between 1858 and 1862, is claimed to be the world's deepest hand-dug well at 392 metres (1,285 ft).[13] The Big Well in Greensburg, Kansas is billed as the world's largest hand-dug well, at 109 feet (33 m) deep and 32 feet (9.8 m) in diameter. However, the Well of Joseph in the Cairo Citadel at 280 feet (85 m) deep and the Pozzo di S. Patrizio (St. Patrick's Well) built in 1527 in Orvieto, Italy, at 61 metres (200 ft) deep by 13 metres (43 ft) wide[14] are both larger by volume.

Driven wells

Driven wells may be very simply created in unconsolidated material with a well hole structure, 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 is encountered, the well is washed of sediment and a pump installed.[15]

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 formation, hence the term drilling.

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). Deeprock rotary drilling method is most common. Rotary can be used in 90% of formation types.

Drilled wells can get water from a much deeper level than dug wells can—often down to several hundred metres.[16]

Drilled wells with electric pumps are used throughout the world, typically in rural or sparsely populated areas, though many urban areas are supplied partly by municipal wells. Most shallow well drilling machines are mounted on large trucks, trailers, or tracked vehicle carriages. Water wells typically range from 3 to 18 metres (10–60 ft) deep, but in some areas can go deeper than 900 metres (3,000 ft).

Well spudder 8606
Cable tool water well drilling rig in Kimball, West Virginia, USA.
AquaBellaPickard-v
Water well drilling in Ein Hemed, near Jerusalem circa 1964

Rotary drilling machines use a segmented steel drilling string, typically made up of 6 m (20 ft) 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 install (by driving or drilling) a steel casing into the well 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 ​14 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 (in air rotary or cable tool drilling) or plastic/PVC (in mud rotary wells, also present in wells drilled into solid rock). The casing is constructed by welding, either chemically or thermally, 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 metres (20 ft) or more in length, and 6 to 12 in (15 to 30 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. 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.

Jet-pump System

An automated water well system powered by a jet-pump.

Submersible-pump System

An automated water well system powered by a submersible pump.

Water System With Cistern

A water well system with a cistern.

Water System With Pressurized Cistern

A water well system with a pressurized cistern.

Screen tube

A section of a stainless steel screen well.

Classification

Water well types wiki
Water well types.

There are two broad classes of drilled-well types, based on the type of aquifer 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 in France).

A special type of water well may be constructed adjacent to freshwater lakes or streams. Commonly called a collector well but sometimes referred to by the trade name Ranney well or Ranney collector, this type of well involves sinking a caisson vertically below the top of the aquifer and then advancing lateral collectors out of the caisson and beneath the surface water body. Pumping from within the caisson induces infiltration of water from the surface water body into the aquifer, where it is collected by the collector well laterals and conveyed into the caisson where it can be pumped to the ground surface.

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 (if the well is not artesian).
  • monitoring wells or piezometers, 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.

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,[17] any available information from nearby wells, geologic maps, and sometimes geophysical imaging.

Contamination

Groundwater Contamination SW Asia Sm
Waterborne diseases can be spread via a well which is contaminated with fecal pathogens from pit latrines
Cleaning a well in Yaounde
Man cleaning a well in Yaoundé, Cameroon.
Hand water pump in India (3382861084)
Hand pump to pump water from a well in a village near Chennai in India, where the well water might be polluted by nearby pit latrines

Shallow pumping wells can often supply drinking water at a very low cost. However, impurities from the surface easily reach shallow sources, which leads to a greater risk of contamination for these wells compared to deeper wells. Contaminated wells can lead to the spread of various waterborne diseases. Dug and driven wells are relatively easy to contaminate; for instance, most dug wells are unreliable in the majority of the United States.[18]

Pathogens

Most of the bacteria, viruses, parasites, and fungi that contaminate well water comes from fecal material from humans and other animals, for example from on-site sanitation systems (such as pit latrines and septic tanks). Common bacterial contaminants include E. coli, Salmonella, Shigella, and Campylobacter jejuni. Common viral contaminants include norovirus, sapovirus, rotavirus, enteroviruses, and hepatitis A and E. Parasites include Giardia lamblia, Cryptosporidium, Cyclospora cayetanensis, and microsporidia.[18]

Chemical contamination

Chemical contamination is a common problem with groundwater.[19] Nitrates from sewage, sewage sludge or fertilizer are a particular problem for babies and young children. Pollutant chemicals include pesticides and volatile organic compounds from gasoline, dry-cleaning, the fuel additive methyl tert-butyl ether (MTBE), and perchlorate from rocket fuel, airbag inflators, and other artificial and natural sources.

Several minerals are also contaminants, including lead leached from brass fittings or old lead pipes, chromium VI from electroplating and other sources, naturally occurring arsenic, radon, and uranium—all of which can cause cancer—and naturally occurring fluoride, which is desirable in low quantities to prevent tooth decay, but can cause dental fluorosis in higher concentrations.[18]

Some chemicals are commonly present in water wells at levels that are not toxic, but can cause other problems. Calcium and magnesium cause what is known as hard water, which can precipitate and clog pipes or burn out water heaters. Iron and manganese can appear as dark flecks that stain clothing and plumbing, and can promote the growth of iron and manganese bacteria that can form slimy black colonies that clog pipes.[18]

Prevention

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 (pit latrines, garbage pits, on-site sewer systems) and carrying out hygiene education. The well should be cleaned with 1% chlorine solution after construction and periodically every 6 months.

Well holes should be covered to prevent loose debris, animals, animal excrement, and wind-blown foreign matter from falling into the hole and decomposing. The cover should be able to be in place at all times, including when drawing water from the well. A suspended roof over an open hole helps to some degree, but ideally the cover should be tight fitting and fully enclosing, with only a screened air vent.

Minimum distances and soil percolation requirements between sewage disposal sites and water wells need to be observed. Rules regarding the design and installation of private and municipal septic systems take all these factors into account so that nearby drinking water sources are protected.

Education of the general population in society also plays an important role in protecting drinking water.

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 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 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.[18]

After the filtration process, it is common to implement an Ultraviolet (UV) system to kill pathogens in the water. UV light effects the DNA of the pathogen by UV-C photons breaking through the cell wall. UV disinfection has been gaining popularity in the past decades as it is a chemical free method of water treatment.[20]

Environmental problems

A risk with the placement of water wells is soil salination which occurs when the water table of the soil begins to drop and salt begins to accumulate as the soil begins to dry out.[21] 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, an asphyxiant, is a chemical compound that is the main component of natural gas. When methane is introduced into a confined space, it displaces oxygen, reducing oxygen concentration to a level low enough to pose a threat to humans and other aerobic organisms but still high enough for a risk of spontaneous or externally caused explosion. This potential for explosion 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.

Lately, however, the described wells/pumps are no longer very efficient and can be replaced by either handpumps or treadle pumps. Another alternative is the use of self-dug wells, electrical deep-well pumps (for higher depths). Appropriate technology organizations as Practical Action are now supplying information on how to build/set-up (DIY) handpumps and treadle pumps in practice.[22][23]

22-alimenti, acqua dolce,Taccuino Sanitatis, Casanatense 418
Water use, Tacuinum Sanitatis, Biblioteca Casanatense (14th century)

Society and culture

Springs and wells have had cultural significance since prehistoric times, leading to the foundation of towns such as Wells and Bath in Somerset. Interest in health benefits led to the growth of spa towns including many with wells in their name, examples being Llandrindod Wells and Royal Tunbridge Wells.

Eratosthenes used a well in his calculation of the circumference of the Earth, sometime around 240 BC, by figuring that the sun must be directly overhead if the head of a person, looking down a well, blocked the sun's reflection. [24]

Many incidents in the Bible take place around wells, such as the finding of a wife for Isaac in Genesis and Jesus's talk with the Samaritan woman in the Gospels.

See also

References

  1. ^ Tegel W, Elburg R, Hakelberg D, Stäuble H, Büntgen U (2012). "Early Neolithic Water Wells Reveal the World's Oldest Wood Architecture". PLoS ONE. 7 (12): e51374. doi:10.1371/journal.pone.0051374. PMC 3526582. PMID 23284685.
  2. ^ Kuhn, Oliver (2004-06-30). "Ancient Chinese Drilling". Canadian Society of Exploration Geophysicists. Canadian Society of Exploration Geophysicists. 29 (6).
  3. ^ Chang, Mingteh (2012). Forest Hydrology: An Introduction to Water and Forests (3rd ed.). CRC Press (published November 1, 2012). p. 31. ISBN 978-1439879948.
  4. ^ Chang, Mingteh (2012). Forest Hydrology: An Introduction to Water and Forests (3rd ed.). CRC Press (published November 1, 2012). p. 31. ISBN 978-1439879948.
  5. ^ Koon, Wee Kek (July 25, 2015). "How the ancient Chinese looked after their drinking water". South China Morning Post.
  6. ^ "Sakieh explication/difference vs Sakia". Britannica.com. Retrieved 2011-12-19.
  7. ^ "Sakia explication". Britannica.com. Retrieved 2011-12-19.
  8. ^ "Stone Age wells found in Cyprus". BBC News.
  9. ^ Ashkenazi, Eli (November 9, 2012). "Ancient Well Reveals Secrets of First Jezreel Valley Farmers". Haaretz.
  10. ^ Kuhn, Oliver (2004-06-30). "Ancient Chinese Drilling". Canadian Society of Exploration Geophysicists. Canadian Society of Exploration Geophysicists. 29 (6).
  11. ^ "ASTM International - Standards Worldwide". www.astm.org.
  12. ^ Joseph P. Riva Jr. and Gordon I. Atwater. "petroleum". Encyclopædia Britannica. Retrieved 2008-06-30.
  13. ^ "Woodingdean Well". 2005. Retrieved 26 Jan 2010.
  14. ^ "St. Patrick's Well". Umbriatravel.com. Retrieved 2011-12-19.
  15. ^ "How I drill a Well." Popular Science, April 1952, pp. 177-181.
  16. ^ Association), NKBA (National Kitchen and Bath (2013-10-29). Kitchen & Bath Residential Construction and Systems. John Wiley & Sons. ISBN 9781118711040.
  17. ^ Du Preez, Michael. "ELECTRO-SEISMIC SURVEYS APPLIED TO MODDELING OF GROUNDWATER FLOW SYSTEMS" (PDF). Bloemfontein, South Africa. Retrieved 21 April 2011.
  18. ^ a b c d e Committee on Environmental Health; Committee on Infectious Diseases (2009). "Drinking water from private wells and risks to children". Pediatrics. 123 (6): 1599–1605. doi:10.1542/peds.2009-0751. PMID 19482772.
  19. ^ Association, American Water Works (2003). Water Sources. American Water Works Association. ISBN 9781583212295.
  20. ^ Meulemans, C. C. E. (1987-09-01). "The Basic Principles of UV–Disinfection of Water". Ozone: Science & Engineering. 9 (4): 299–313. doi:10.1080/01919518708552146. ISSN 0191-9512.
  21. ^ "Soil salination by placement of water wells mentioned in India". Ngm.nationalgeographic.com. 2002-10-17. Retrieved 2011-12-19.
  22. ^ "Practical Answers – Handpumps". Practicalaction.org. Retrieved 2011-12-19.
  23. ^ "Treadle pump". Dev.practicalaction.org. Retrieved 2011-12-19.
  24. ^ Astronomy 101 Specials: Eratosthenes and the Size of the Earth

Bibliography

  • Driscoll, F. (1986). Groundwater and Wells. St. Paul: Johnson Filtration Systems. ISBN 978-0-9616456-0-1.
  • Raymond Rowles (1995). Drilling for Water (2nd ed.). Avebury, Cranfield University. ISBN 1-85628-984-2.

External links

Aquifer

An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). Groundwater can be extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude (or aquifuge), which is a solid, impermeable area underlying or overlying an aquifer. If the impermeable area overlies the aquifer, pressure could cause it to become a confined aquifer.

Bibsys

BIBSYS is an administrative agency set up and organized by the Ministry of Education and Research in Norway. They are a service provider, focusing on the exchange, storage and retrieval of data pertaining to research, teaching and learning – historically metadata related to library resources.

BIBSYS are collaborating with all Norwegian universities and university colleges as well as research institutions

and the National Library of Norway. Bibsys is formally organized as a unit at the Norwegian University of Science and Technology (NTNU), located in Trondheim, Norway. The board of directors is appointed by Norwegian Ministry of Education and Research.

BIBSYS offer researchers, students and others an easy access to library resources by providing the unified search service Oria.no and other library services.

They also deliver integrated products for the internal operation for research and special libraries as well as open educational resources.

As a DataCite member BIBSYS act as a national DataCite representative in Norway and thereby allow all of Norway's higher education and research institutions to use DOI on their research data.

All their products and services are developed in cooperation with their member institutions.

Cameo appearance

A cameo role or cameo appearance (; often shortened to just cameo) is a brief appearance or voice part of a well known person in a work of the performing arts. These roles are generally small, many of them non-speaking ones, and are commonly either appearances in a work in which they hold some special significance (such as actors from an original movie appearing in its remake) or renowned people making uncredited appearances. Short appearances by celebrities, film directors, politicians, athletes or musicians are common. A crew member of the movie or show playing a minor role can be referred to as a cameo as well, such as Alfred Hitchcock's frequently performed cameos.

Charles VII of France

Charles VII (22 February 1403 – 22 July 1461), called the Victorious (French: le Victorieux) or the Well-Served (French: le Bien-Servi), was King of France from 1422 to his death in 1461, the fifth from the House of Valois.

In the midst of the Hundred Years' War, Charles VII inherited the throne of France under desperate circumstances. Forces of the Kingdom of England and the Duchy of Burgundy occupied Guyenne and northern France, including Paris, the most populous city, and Reims, the city in which the French kings were traditionally crowned. In addition, his father Charles VI had disinherited him in 1420 and recognized Henry V of England and his heirs as the legitimate successors to the French crown instead. At the same time, a civil war raged in France between the Armagnacs (supporters of the House of Valois) and the Burgundian party (supporters of the House of Valois-Burgundy allied to the English).

With his court removed to Bourges, south of the Loire River, Charles was disparagingly called the “King of Bourges”, because the area around this city was one of the few remaining regions left to him. However, his political and military position improved dramatically with the emergence of Joan of Arc as a spiritual leader in France. Joan of Arc and other charismatic figures led French troops to lift the siege of Orléans, as well as other strategic cities on the Loire river, and to crush the English at the battle of Patay. With the local English troops dispersed, the people of Reims switched allegiance and opened their gates, which enabled the coronation of Charles VII in 1429 at Reims Cathedral. This long-awaited event boosted French morale as hostilities with England resumed. Following the battle of Castillon in 1453, the French expelled the English from all their continental possessions except for the Pale of Calais.

The last years of Charles VII were marked by conflicts with his turbulent son, the future Louis XI of France.

Euphoria

Euphoria ( (listen)) is the experience (or affect) of pleasure or excitement and intense feelings of well-being and happiness. Certain natural rewards and social activities, such as aerobic exercise, laughter, listening to or making music, and dancing, can induce a state of euphoria. Euphoria is also a symptom of certain neurological or neuropsychiatric disorders, such as mania. Romantic love and components of the human sexual response cycle are also associated with the induction of euphoria. Certain drugs, many of which are addictive, can cause euphoria, which at least partially motivates their recreational use.Hedonic hotspots – i.e., the pleasure centers of the brain – are functionally linked. Activation of one hotspot results in the recruitment of the others. Inhibition of one hotspot results in the blunting of the effects of activating another hotspot. Therefore, the simultaneous activation of every hedonic hotspot within the reward system is believed to be necessary for generating the sensation of an intense euphoria.

Happiness

Happiness is used in the context of mental or emotional states, including positive or pleasant emotions ranging from contentment to intense joy. It is also used in the context of life satisfaction, subjective well-being, eudaimonia, flourishing and well-being.Since the 1960s, happiness research has been conducted in a wide variety of scientific disciplines, including gerontology, social psychology, clinical and medical research and happiness economics.

Health

Health, as defined by the World Health Organization (WHO), is "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity." This definition has been subject to controversy, as it may have limited value for implementation. Health may be defined as the ability to adapt and manage physical, mental and social challenges throughout life.

Health care

Health care or healthcare is the maintenance or improvement of health via the prevention, diagnosis, and treatment of disease, illness, injury, and other physical and mental impairments in people. Health care is delivered by health professionals (providers or practitioners) in allied health fields. Physicians and physician associates are a part of these health professionals. Dentistry, midwifery, nursing, medicine, optometry, audiology, pharmacy, psychology, occupational therapy, physical therapy and other health professions are all part of health care. It includes work done in providing primary care, secondary care, and tertiary care, as well as in public health.

Access to health care may vary across countries, communities, and individuals, largely influenced by social and economic conditions as well as health policies. Health care systems are organizations established to meet the health needs of targeted populations. According to the World Health Organization (WHO), a well-functioning health care system requires a financing mechanism, a well-trained and adequately paid workforce, reliable information on which to base decisions and policies, and well maintained health facilities to deliver quality medicines and technologies.An efficient health care system can contribute to a significant part of a country's economy, development and industrialization. Health care is conventionally regarded as an important determinant in promoting the general physical and mental health and well-being of people around the world. An example of this was the worldwide eradication of smallpox in 1980, declared by the WHO as the first disease in human history to be completely eliminated by deliberate health care interventions.

Hydraulic fracturing

Hydraulic fracturing (also fracking, fraccing, frac'ing, hydrofracturing or hydrofracking) is a well stimulation technique in which rock is fractured by a pressurized liquid. The process involves the high-pressure injection of 'fracking fluid' (primarily water, containing sand or other proppants suspended with the aid of thickening agents) into a wellbore to create cracks in the deep-rock formations through which natural gas, petroleum, and brine will flow more freely. When the hydraulic pressure is removed from the well, small grains of hydraulic fracturing proppants (either sand or aluminium oxide) hold the fractures open.Hydraulic fracturing began as an experiment in 1947, and the first commercially successful application followed in 1950. As of 2012, 2.5 million "frac jobs" had been performed worldwide on oil and gas wells; over one million of those within the U.S. Such treatment is generally necessary to achieve adequate flow rates in shale gas, tight gas, tight oil, and coal seam gas wells. Some hydraulic fractures can form naturally in certain veins or dikes.Hydraulic fracturing is highly controversial in many countries. Its proponents advocate the economic benefits of more extensively accessible hydrocarbons,

as well as replacing coal with gas, which is cleaner and emits less carbon dioxide (CO2). Opponents argue that these are outweighed by the potential environmental impacts, which include risks of ground and surface water contamination, air and noise pollution, and the triggering of earthquakes, along with the consequential hazards to public health and the environment.Methane leakage is also a problem directly associated with hydraulic fracturing, as a Environmental Defense Fund (EDF) report in the US highlights, where the leakage rate in Pennsylvania during extensive testing and analysis was found to be approximately 10%, or over five times the reported figures. This leakage rate is considered representative of the hydraulic fracturing industry in the US generally. The EDF have recently announced a satellite mission to further locate and measure methane emissions.Increases in seismic activity following hydraulic fracturing along dormant or previously unknown faults are sometimes caused by the deep-injection disposal of hydraulic fracturing flowback (a byproduct of hydraulically fractured wells), and produced formation brine (a byproduct of both fractured and nonfractured oil and gas wells). For these reasons, hydraulic fracturing is under international scrutiny, restricted in some countries, and banned altogether in others. The European Union is drafting regulations that would permit the controlled application of hydraulic fracturing.

List of TCP and UDP port numbers

This is a list of TCP and UDP port numbers used by protocols of the application layer of the Internet protocol suite for the establishment of host-to-host connectivity.

The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) needed only one port for full-duplex, bidirectional traffic. The Stream Control Transmission Protocol (SCTP) and the Datagram Congestion Control Protocol (DCCP) also use port numbers. They usually use port numbers that match the services of the corresponding TCP or UDP implementation, if they exist.

The Internet Assigned Numbers Authority (IANA) is responsible for maintaining the official assignments of port numbers for specific uses. However, many unofficial uses of both well-known and registered port numbers occur in practice. Similarly many of the official assignments refer to protocols that were never or are no longer in common use. This article lists port numbers and their associated protocols that have experienced significant uptake.

Mental health

Mental health is defined as the level of psychological well-being or an absence of mental illness. It is the state of someone who is "functioning at a satisfactory level of emotional and behavioural adjustment". From the perspectives of positive psychology or of holism, mental health may include an individual's ability to enjoy life, and to create a balance between life activities and efforts to achieve psychological resilience.

According to the World Health Organization (WHO), mental health includes "subjective well-being, perceived self-efficacy, autonomy, competence, inter-generational dependence, and self-actualization of one's intellectual and emotional potential, among others." The WHO further states that the well-being of an individual is encompassed in the realization of their abilities, coping with normal stresses of life, productive work and contribution to their community.

Cultural differences, subjective assessments, and competing professional theories all affect how one defines "mental health".

Oil well

An oil well is a boring in the Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released along with the oil. A well that is designed to produce only gas may be termed a gas well.

Playwright

A playwright or dramatist (rarely dramaturge) is a person who writes plays.

Positive psychology

Positive psychology is "the scientific study of what makes life most worth living", or "the scientific study of positive human functioning and flourishing on multiple levels that include the biological, personal, relational, institutional, cultural, and global dimensions of life". Positive psychology is concerned with eudaimonia, "the good life", reflection about what holds the greatest value in life – the factors that contribute the most to a well-lived and fulfilling life.

Positive psychology began as a new domain of psychology in 1998 when Martin Seligman chose it as the theme for his term as president of the American Psychological Association. Mihaly Csikszentmihalyi, Christopher Peterson and Barbara Fredrickson are regarded as co-initiators of this development. It is a reaction against psycho-analysis and behaviorism, which have focused on "mental illness", meanwhile emphasising maladaptive behavior and negative thinking. It builds further on the humanistic movement, which encouraged an emphasis on happiness, well-being, and positivity, thus creating the foundation for what is now known as positive psychology.Positive psychologists have suggested a number of ways in which individual happiness may be fostered. Social ties with a spouse, family, friends and wider networks through work, clubs or social organisations are of particular importance, while physical exercise and the practice of meditation may also contribute to happiness. Happiness may rise with increasing financial income, though it may plateau or even fall when no further gains are made.

Quality of life

Quality of life (QOL) is an overarching term for the quality of the various domains in life. It is a standard level that consists of the expectations of an individual or society for a good life. These expectations are guided by the values, goals and socio-cultural context in which an individual lives. It is a subjective, multidimensional concept that defines a standard level for emotional, physical, material and social well-being. It serves as a reference against which an individual or society can measure the different domains of one’s own life. The extent to which one's own life coincides with this desired standard level, put differently, the degree to which these domains give satisfaction and as such contribute to one's subjective well-being, is called life satisfaction.

Trademark

A trademark, trade mark, or trade-mark is a recognizable sign, design, or expression which identifies products or services of a particular source from those of others, although trademarks used to identify services are usually called service marks. The trademark owner can be an individual, business organization, or any legal entity. A trademark may be located on a package, a label, a voucher, or on the product itself. For the sake of corporate identity, trademarks are often displayed on company buildings. It is legally recognized as a type of intellectual property.

The first legislative act concerning trademarks was passed in 1266 under the reign of Henry III, requiring all bakers to use a distinctive mark for the bread they sold. The first modern trademark laws emerged in the late 19th century. In France the first comprehensive trademark system in the world was passed into law in 1857. The Trade Marks Act 1938 of the United Kingdom changed the system, permitting registration based on "intent-to-use”, creating an examination based process, and creating an application publication system. The 1938 Act, which served as a model for similar legislation elsewhere, contained other novel concepts such as "associated trademarks", a consent to use system, a defensive mark system, and non claiming right system.

The symbols ™ (the trademark symbol) and ® (the registered trademark symbol) can be used to indicate trademarks; the latter is only for use by the owner of a trademark that has been registered.

Tyga

Micheal Ray Stevenson (born November 19, 1989), known by his stage name Tyga (a backronym for Thank you God always), is an American rapper, songwriter, singer, actor and television personality. In 2011, Tyga signed a recording contract with Young Money Entertainment, Cash Money Records and Republic Records. His major label debut Careless World: Rise of the Last King, included the singles "Rack City", "Faded" featuring fellow Young Money artist Lil Wayne, "Far Away" featuring Chris Richardson, "Still Got It" featuring Drake, and "Make It Nasty". He released his third album Hotel California, on April 9, 2013, and includes the singles "Dope" featuring Rick Ross, "For The Road" featuring Chris Brown, and "Show You" featuring Future. His 2018 single, "Taste" featuring Offset, peaked at number 8 on the Billboard Hot 100, being his first Top 40 single since "Ayo" with Chris Brown in 2015.

XML

Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The W3C's XML 1.0 Specification and several other related specifications—all of them free open standards—define XML.The design goals of XML emphasize simplicity, generality, and usability across the Internet. It is a textual data format with strong support via Unicode for different human languages. Although the design of XML focuses on documents, the language is widely used for the representation of arbitrary data structures such as those used in web services.

Several schema systems exist to aid in the definition of XML-based languages, while programmers have developed many application programming interfaces (APIs) to aid the processing of XML data.

Yggdrasil

Yggdrasil (from Old Norse Yggdrasill) is an immense mythical tree that plays a central role in Norse cosmology, where it connects the Nine Worlds.

Yggdrasil is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson. In both sources, Yggdrasil is an immense ash tree that is center to the cosmos and considered very holy. The gods go to Yggdrasil daily to assemble at their things, traditional governing assemblies. The branches of Yggdrasil extend far into the heavens, and the tree is supported by three roots that extend far away into other locations; one to the well Urðarbrunnr in the heavens, one to the spring Hvergelmir, and another to the well Mímisbrunnr. Creatures live within Yggdrasil, including the dragon Níðhöggr, an unnamed eagle, and the stags Dáinn, Dvalinn, Duneyrr and Duraþrór.

Conflicting scholarly theories have been proposed about the etymology of the name Yggdrasill, the possibility that the tree is of another species than ash, its connection to the many sacred trees and groves in Germanic paganism and mythology, and the fate of Yggdrasil during the events of Ragnarök.

Soil
Foundations
Retaining walls
Stability
Earthquakes
Geosynthetics
Numerical analysis

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