Which type of aquifer has an impermeable dirt/rock layer that prevents water from seeping into the aquifer from the ground surface located directly above?

• A. Unconfined
• B. Perched
• C. Confined
• D. Artesian

Answer: (C)

Having an impermeable layer directly above an aquifer creates a cap that stops surface water from seeping down to recharge the aquifer. The water is trapped between that cap and another boundary, so it’s under pressure and cannot freely rise or be recharged from the surface. This setup defines a confined aquifer.

Unconfined aquifers have no such impermeable cap above them, so rainfall can infiltrate directly. A perched aquifer sits on a localized impermeable layer above the main aquifer, forming a small, separate unit. Artesian describes the pressure state of water in a confined aquifer, not the mere presence of an overhead impermeable layer.