What is the main feature of an artesian well?

The main feature of an artesian well is that it is characterized by pressurized water that flows upwards naturally without the need for pumping. This occurs when groundwater is confined beneath a layer of impermeable rock or sediment, creating pressure in the aquifer. When a well is drilled into this pressurized aquifer, the water is pushed to the surface, sometimes reaching above the ground level. This unique characteristic distinguishes artesian wells from other types of wells where water must be extracted through mechanical means.

The other options do not accurately represent the defining elements of an artesian well. A well that is always dry does not serve any purpose related to artesian characteristics. A well with a static water level refers to the water being at a consistent height, which is not necessarily indicative of artesian properties. A manually dug well does not imply any specific hydraulic pressure or flow characteristics related to artesian wells. Thus, the defining feature of an artesian well is the natural upward flow of pressurized water.