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Village Pump redirects here, for information on Wikipedia project-related discussions, see .A water well is an artificial excavation or structure put down by any method such as digging, boring or drilling for the purposes of withdrawing water from underground aquifers.
Types of water wells
Dug wells Until recent centuries, all artificial wells were pumpless dug wells of varying degrees of formality. Their indispensibility has produced numerous literary references, literal and figurative, to them, including the Christian Bible story of Jesus meeting a woman at Jacob's well (John 4:6) and the "Ding Dong Bell" nursery rhyme about a cat in a well. In India, stepwells were created at times, sometimes used both for water and for cooling. Such primitive dug wells were excavations with diameters large enough to accommodate muscle-powered digging to below the water table. Relatively formal versions tended to be lined with laid stones or brick; extending this lining into a wall around the well presumably served to reduce both contamination and injuries by falling into the well. The iconic American farm well features a peaked roof above the wall, reducing airborne contamination, and a cranked windlass, mounted between the two roof-supporting members, for raising and lowering a bucket to obtain water. More modern dug wells may be hand-pumped, especially in undeveloped and third-world countries. Note that the term "shallow well" is not a synonym for dug well, and may actually be quite deep - see Aquifer type, below. Drilled wells Drilled wells, also referred to as tube-wells, can access water from a much deeper level by mechanical drilling. Narrow-diameter drilled wells with electric pumps are currently used in the U.S. and other more developed countries, typically in rural or sparsely populated areas. These wells are likely to be created with specialized earth-moving equipment, and are usually lined with a casing composed of factory-made cylindrical concrete shells, synthetic (PVC) plastic water pipe, or steel pipe , or a combination of these materials. The casing is constructed by lowering lengths of this material into the excavated well, vertically stacked with their ends nested. The sections of casing are usually 12' or more in length, and 6" - 12" in diameter, depending on the intended use of the well and local ground water conditions. In such an installation, excavated earth, gravel and/or masonry grout is packed around the casing after its placement, and a concrete or steel disc is used to cover the opening of the well above ground. Water enters the well primarily by oozing out of the earth into either a constructed screen or open borehole placed at the bottom end of the casing; the gravel is commonly packed around screen material to help filter the water of sand and earth, helping to clarify the ground water entering the well. Driven wells may be created in unconsolidated material with a "well point", which consists of a hardened drive point and a screen. The point is simply driven 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. This is the cheapest and simplest type of water well known today, however it is only useful at relatively shallow depths and for small capacity wells. Aquifer classification Two broad classes of drilled-well types may be distinguished, based on the type of aquifer which the well is completed in: There clearly are many cases that fall in between these two endmembers; oftentimes unconfined wells may be very deep (what is often called a shallow well can be over 150 m deep) and many times wells are completed across all aquifers from their top to their bottom (especially agricultural or industrial wells), being open to both unconfined and confined aquifers. Use classification Two additional broad classes of well types may be distinguished, based on the use of the well: 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. Drawing Water
Contamination Shallow pumping wells can often supply drinking water 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. In shallow and deep wells, the water requires pumping to the surface; in artesian wells, conversely, water usually rises to a greater level than the land surface when extracted from a deep source. 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 boil the water (although, unless in contact with surface water or near areas where treated wastewater is being recharged, groundwater tends to be free of microorganisms). Contamination related to human activity is a common problem with groundwater. For example, "BTEX" (benzene, toluene, ethylbenzene and xylene), which comes from gasoline refining, and MTBE, which is a fuel additive, are common contaminants in urbanized areas, often as the result of leaking underground storage tanks. Many industrial solvents also are common groundwater contaminants, often as the result of dumping. Cleanup of contaminated groundwater tends to be very costly. Effective remediation of water supply is generally very difficult. Setting up a well Before deciding to install a well, one should first see if there are aquifers in the area intended for drilling. In the United States, such specialized documents are prepared by the USGS and EPA. Ancient technologies Australian Aborigines relied on wells to survive the harsh Australian desert. They would dig down, scooping out sand and mud to reach clean water, then cover the source with spinifex to prevent spoliation. White people call these native wells or soaks. The earliest wells are known from the Neolithic. In the submerged Pre-Pottery Neolithic B settlement of Atlit Yam in Israel, 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 and maybe shallower examples from Shillourokambos as well. Wood-lined wells are known from the early Neolithic Linearbandkeramic culture, for example in Kückhoven, dated 5090BC and Eythra), dated 5200BC in Germany and Schletz in Austria. The early Mesolithic site of Friesack in Germany has yielded a shallow pit with the remains of a birch-bark container that may have been a shallow artificial well as well. From the Iron Age onwards, wells are common archaeological features, both with wooden shafts and shaft-linings made from wickerwork. See also | ||||||||||||
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