What defines an artesian well?

An artesian well is characterized by the unique condition where the water level rises above the initial encounter point, typically due to the hydrostatic pressure present in the aquifer from which it draws water. This pressure forces the water to rise through the wellbore without the need for pumping, often causing the water to flow freely to the surface. The geological conditions that allow this phenomenon involve a confined aquifer where impermeable layers above and below trap the water, creating pressure that results in the characteristic rise of the water within the well.

In contrast, a well that yields hot water defines a geothermal well and is not related to the specific definition of artesian wells. A capped well refers to a well that is sealed at its top, which does not describe the pressure or water level dynamics. Lastly, the description of a well that drains into an aquifer pertains to a different type of well interaction with groundwater systems, rather than the pressure dynamics that define an artesian well.