artesian well

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artesian well, deep drilled well through which water is forced upward under pressure. The water in an artesian well flows from an aquifer, which is a layer of very porous rock or sediment, usually sandstone, capable of holding and transmitting large quantities of water. The geologic conditions necessary for an artesian well are an inclined aquifer sandwiched between impervious rock layers above and below that trap water in it. Water enters the exposed edge of the aquifer at a high elevation and percolates downward through interconnected pore spaces. The water held in these spaces is under pressure because of the weight of water in the portion of the aquifer above it. If a well is drilled from the land surface through the overlying impervious layer into the aquifer, this pressure will cause the water to rise in the well. In areas where the slope of the aquifer is great enough, pressure will drive the water above ground level in a spectacular, permanent fountain. Artesian springs can occur in similar fashion where faults or cracks in the overlying impervious layer allow water to flow upward. Water from an artesian well or spring is usually cold and free of organic contaminants, making it desirable for drinking. In North America, the Dakota sandstone provides aquifers for an artesian system that underlies parts of the Dakotas, Montana, Wyoming, Kansas, Nebraska, and Saskatchewan and supplies great quantities of water to the dry Great Plains region. Many East Coast cities derive their water supplies from aquifers that are exposed along the edge of the Piedmont and dip downward toward the Atlantic coast. The largest artesian system in the world underlies nearly all of E and S Australia. Other important artesian systems serve London, Paris, and E Algeria.

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artesian water Groundwater that is confined in an aquifer, but which may overflow on to the land surface via artificial boreholes or, sometimes, natural springs, because of the high hydraulic head that may be developed in a confined aquifer. Artesian conditions are common when the aquifer has a synclinal form. The London Basin, England, provided artesian water during the nineteenth century from a chalk aquifer sealed by clays. The term is derived from the Artois region of north-western France.

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artesian water Groundwater that is confined in an aquifer, but which may overflow on to the land surface via artificial boreholes or, sometimes, natural springs, because of the high hydraulic head that may be developed in a confined aquifer. Artesian conditions are common when the aquifer has a synclinal form. The London Basin, England, provided artesian water during the nineteenth century from a chalk aquifer sealed by clays. The term is derived from the Artois region of north-western France.

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artesian water Ground water that originally is confined in an aquifer and that reaches the land surface owing to the high hydraulic pressure that may be developed in a confined aquifer when this has a synclinal form. The London Basin, England, provided artesian water during the nineteenth century from a chalk aquifer sealed by clays. Many desert oases are created by the emergence of artesian water in springs or pools.

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artesian well (overflowing well) A well that flows at the surface without pumping, because it is sunk into a confined aquifer whose hydraulic head (sometimes called the potentiometric or piezometric head) lies above ground level. See AQUIFER; and ARTESIAN WATER.

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artesian well(overflowing well) A well that flows at the surface without pumping, because it is sunk into a confined aquifer whose hydraulic head (sometimes called the potentiometric or piezometric head) lies above ground level. See artesian water.

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Artesian well

A well that discharges water held in a confined aquifer . Artesian wells are usually thought of as wells whose water is free flowing at the land surface. However, there are many other natural systems that can result in such wells. The classic concept of artesian flow involves a basin with a water-intake area above the level of groundwater discharge . These systems can include stabilized sand dunes ; fractured zones along bedrock faults; horizontally layered rock formations; and the intermixing of permeable and impermeable materials along glacial margins.

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artesian well Well from which water is forced out naturally under pressure. Artesian wells are bored where water in a layer of porous rock is sandwiched between two layers of impervious rock. The water-filled layer is called an aquifer. Water flows up to the surface because distant parts of the aquifer are higher than the well-head.