| a well in which water rises under pressure from a permeable stratum overlaid by impermeable rock. |
ar·te·sian well  (är-tē'zhən)   (click for larger image in new window) n. A well drilled through impermeable strata to reach water capable of rising to the surface by internal hydrostatic pressure. [French artésien, from Old French artesien, of Artois, from Arteis, Artois, France.] |
artesian well
a man-made spring from which water flows under natural pressure without pumping. It is dug or drilled wherever a gently dipping, permeable rock layer (such as sandstone) receives water along its outcrop at a level higher than the level of the surface of the ground at the well site. At the outcrop the water moves down into the aquifer (water-bearing layer) but is prevented from leaving it by impermeable rock layers (such as shale) above and below it. Pressure from the water's weight (hydrostatic pressure) forces water to the surface of a well drilled down into the aquifer; the pressure for the steady upflow is maintained by the continuing penetration of water into the aquifer at the intake area.
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