How can an artesian aquifer raise water to the surface without pumping?

An artesian aquifer can raise water to the surface without pumping due to natural hydrostatic pressure. This process occurs when a permeable rock layer, such as sandstone, acts as an aquifer and is trapped between two impermeable layers, such as shale.12

The system functions because the aquifer receives water at an intake area—often an outcrop—located at a higher elevation than the ground level at the well site. As water moves down into the aquifer, it is confined by the impermeable layers above and below it. The weight of this water creates hydrostatic pressure, which forces the water upward through a well drilled into the aquifer. This steady upflow is maintained as long as the aquifer continues to receive water at the higher intake area. If the overlying impermeable rock is broken by faults or joints, the water may also escape naturally to the surface as an artesian spring.12