Confined Aquifer and its Characteristics

A confined aquifer, also known as an artesian aquifer, is a type of groundwater system that is characterized by the presence of an impermeable layer above and below the aquifer. This impermeable layer restricts the movement of water into and out of the aquifer, creating a confined or pressurized system.

Phreatic Zone
The phreatic zone, also known as the saturated zone, refers to the region within an aquifer where all the pore spaces are filled with water. This zone exists in both confined and unconfined aquifers. In an unconfined aquifer, the water table represents the upper boundary of the phreatic zone. However, in a confined aquifer, the water table does not exist as the aquifer is overlain by an impermeable layer. Instead, the water in the confined aquifer is under pressure and is referred to as the confined or artesian water.

Piezometric Surface
The piezometric surface, also known as the potentiometric surface, represents the level to which water will rise in a well or piezometer that taps into a confined aquifer. It is a hypothetical surface that represents the pressure head of the confined water. The piezometric surface is a key parameter in understanding the flow of water within a confined aquifer.

Free Water Table
The free water table represents the upper boundary of the phreatic zone in an unconfined aquifer. It is the level at which the water pressure is equal to atmospheric pressure. In an unconfined aquifer, the water table fluctuates with changes in recharge and discharge, and it can be observed directly in wells or through the presence of surface water bodies such as lakes or rivers.

Free Flowing Well
A free flowing well is a well that taps into an unconfined aquifer where the water table is above the ground surface. In this case, water can naturally flow to the surface under its own pressure without the need for pumping. The free flowing well is a common feature in unconfined aquifers where the water table is close to the ground surface.

Conclusion
In summary, a confined aquifer is not associated with the phreatic zone (option A) because the phreatic zone is a characteristic of both confined and unconfined aquifers, whereas confined aquifers have a different water table concept known as the piezometric surface. Confined aquifers are characterized by the presence of impermeable layers above and below the aquifer, creating a pressurized system where water is under pressure and does not exhibit a free water table or free flowing wells.