Artesian aquifer




 * 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 a 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 defies gravity and goes up instead of down.

Why is a well 'artesian' ?


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:


 * $$P = \rho \cdot g \cdot (z_\mathrm{recharge}-z_\mathrm{wellhead})$$

where $$\rho$$ (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 (zr &minus; zw).

"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. The technique was also known much earlier in Syria and Egypt, although whether the monks of Artois learned of it from outside sources, or discovered it independently, is unknown.

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: Artesian Water Well System)
 * Fountain Point, Michigan
 * Olympia, Washington
 * Memphis, Tennessee (World's largest
 * Smoke Hole Caverns, Seneca Rocks, West Virginia