Artesian aquifer

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See Great Artesian Basin for the water source in Australia.
Geological strata giving rise to an artesian well.
Schematic of an artesian well
US Navy Seabees tapping an artesian well in Helmand Province, Afghanistan

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.

A well drilled into such an aquifer is called an artesian well if water reaches the ground surface under the natural pressure of the aquifer, in which case the well is called a flowing artesian well.[1]

An aquifer is a geologic layer of porous and permeable material such as sand and gravel, limestone, or sandstone, through which water flows and is stored. An artesian aquifer is confined between impermeable rocks or clay which causes this positive pressure. Not all the aquifers are artesian, because the water table must reach the surface (not the case for underground groundwater such as, for example, the Nubian Sandstone Aquifer System). The recharging of aquifers happens when the water table at its recharge zone is at a higher elevation than the head of the well.

Fossil water aquifers can also be artesian if they are under sufficient pressure from the surrounding rocks. This is similar to how many newly tapped oil wells are pressurized.

Artesian wells were named after the former province of Artois in France, where many artesian wells were drilled by Carthusian monks from 1126.[2]

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Notes

  1. ^ Wheeler, H. W (1980), Artesian bores of South Australia : an annotated photographic record, 1939-1948, Pioneer Books, ISBN 978-0-908065-06-6  and Federal Water Resources Assistance Program (Australia); New South Wales. Department of Water Resources. Technical Services Division; Australian Water Resources Council. Interstate Working Group on the Great Artesian Basin (1990), Specification for construction, reconditioning or plugging of bores tapping recognised aquifers of the Great Artesian Basin in New South Wales (1st ed ed.), Dept. of Water Resources, Technical Services Division, retrieved 19 January 2014 
  2. ^ Frances Gies and Joseph Gies, Cathedral, Forge, and Waterwheel subtitled "Technology and Invention in the Middle Ages". Harper Perennial, 1995 ISBN 0-06-016590-1, page 112.

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