An artesian aquifer could occur in a(n):

• A. Unconfined aquifer
• B. Confined aquifer
• C. Shallow aquifer
• D. Deep well

Answer: (B)

An artesian aquifer specifically refers to a type of confined aquifer where groundwater is trapped under pressure between layers of less permeable material, such as clay or rock. This pressure drives the water in the aquifer to rise above the level of the aquifer itself when a well is drilled into it, often resulting in the water flowing freely to the surface.

The nature of confined aquifers allows for this phenomenon, as the layers surrounding the aquifer prevent water from easily escaping and maintain the pressure needed for artesian flow. In contrast, unconfined aquifers do not have this layer of impermeable material above them, and thus, they do not exhibit artesian characteristics. Shallow aquifers and deep wells are descriptions of aquifer depth and well type but don’t specifically pertain to the conditions that create an artesian aquifer. Therefore, the unique qualities of a confined aquifer are critical to the understanding of artesian conditions.