Artesian_well

Geological strata giving rise to an Artesian well.

See Great Artesian Basin for the water source in Australia.

An artesian aquifer is a confined aquifer containing groundwater that will flow upwards out of a well without the need for pumping. An aquifer provides the water for an artesian well. An aquifer is a layer of soft rock, like limestone or sandstone, that absorbs water from an inlet path. Porous stone is crushed between impermeable rocks or clay. This keeps the pressure high, so when the water finds a hole, it overcomes gravity and goes up instead of down.

Contents 1 Why is a well \'artesian\' ? 2 Origin 3 Examples of artesian wells 3.1 Australia 3.2 North America 4 See also 5 Notes

Why is a well \'artesian\' ?

An artesian well.

In recharging aquifers, this happens because the water table at its recharge zone is at a higher elevation than the head of the well.

Pascal\'s law predicts the theoretical hydrostatic pressure P:

$P\; =\; \backslash rho\; \backslash cdot\; g\; \backslash cdot\; (z\_\backslash mathrm\{recharge\}-z\_\backslash mathrm\{wellhead\})$

where $\backslash rho$ (rho) is the density of the fluid, g the acceleration due to gravity, and z is the elevation. In practical terms the pressure is expressed as metres water column (z_r − z_w).

"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.

Origin

Artesian wells were named after the former province of Artois in France, where many artesian wells were drilled by Carthusian monks since 1126.Frances 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. The technique was also known much earlier in Syria and Egypt,For references on ancient uses, see Michel Wuttmann, "The Qanats of \'Ayn-Manâwîr, Kharga Oasis, Egypt", in Jasr 2001, p. 1. and Discoveries in the Western Desert of Egypt although whether the monks of Artois learned of it from outside sources or discovered it independently is unknown.

Examples of artesian wells

Australia

• The Great Artesian Basin is the largest and deepest artesian basin in the world, occupying 23% of the continent.

North America

Some towns in the United States were named Artesia after the artesian wells in the vicinity. Other artesian well sites include:

• Fountain Point, Michigan
• Olympia, Washington
• Memphis, Tennessee
• Smoke Hole Caverns, Seneca Rocks, West Virginia

See also

• Drinking water
• Fluid mechanics
• Great Artesian Basin
• Hydrogeology
• Qanat

Notes

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