An artesian well is simply a well that doesn't require a pump to bring water to the surface. This occurs when there is enough positive pressure in the aquifer to bring the water to the surface. An artesian aquifer is confined between impermeable rocks or clay which causes this positive pressure.

Where do artesian wells occur?

Artesian wells occur naturally over large areas of the Santa Clara Valley, and flowing artesian wells have been observed since the 1850s. When pressures in groundwater aquifers are high, old lost wells may begin flowing freely at the land surface. This wastes water and can create nuisance conditions.

How artesian well is formed?

An artesian aquifer is trapped water, surrounded by layers of impermeable rocks or clay, which applies positive pressure to the water contained within the aquifer. ... If water reaches the ground surface under the natural pressure of the aquifer, the well is termed a flowing artesian well.