How is an artesian well defined?

An artesian well is characterized by water being able to rise to the surface naturally due to the confining pressure of the aquifer that it taps into. This pressure results from the water being trapped between layers of impermeable rock or clay, creating a pressurized environment. When a well is drilled into this confined aquifer, the internal pressure can force the water up the well casing, potentially reaching the surface without the need for pumping. This phenomenon distinguishes artesian wells from other types of wells, where water typically needs to be mechanically extracted.

The other definitions provided do not accurately capture the essential feature of an artesian well. For instance, the concept of low pressure does not align with the characteristics of artesian wells since they specifically involve high pressure that pushes water upward. Additionally, the method of construction—whether the well is hand-dug or drilled—doesn't define an artesian well. Finally, artesian wells do not require an external power source for water extraction, as the natural pressure can often provide sufficient force for water to flow.