An artesian well is a
well that brings
groundwater to the surface without pumping because it is under pressure within a body of rock and/or sediment known as an
aquifer.[1] When trapped water in an aquifer is surrounded by layers of
impermeable rock or clay, which apply positive pressure to the water, it is known as an artesian aquifer.[1] If a well were to be sunk into an artesian aquifer, water in the well-pipe would rise to a height corresponding to the point where
hydrostatic equilibrium is reached.[1]
A well drilled into such an aquifer is called an artesian well.[1] If water reaches the ground surface under the natural pressure of the aquifer, the well is termed a flowing artesian well.[2][3]
Fossil water aquifers can also be artesian if they are under sufficient pressure from the surrounding rocks, similar to how many newly tapped
oil wells are pressurized.
Not all aquifers are artesian (i.e., water table aquifers occur where the groundwater level at the top of the aquifer is at equilibrium with atmospheric pressure). The recharging of aquifers happens when the water table at its recharge zone is at a higher
elevation than the head of the well.
History
The first mechanically accurate explanation for artesian wells was given by
Al-Biruni.[4] Artesian wells were named after the former province of
Artois in
France, where many artesian wells were drilled by
Carthusian monks from 1126.[5]