An unconfined aquifer is best described as:

• A. A An aquifer protected by an impermeable layer
• B. B An aquifer that is entirely below the groundwater table
• C. C An unconfined aquifer that receives water directly from the ground surface above
• D. D An aquifer that is not influenced by rainfall

Answer: (C)

An unconfined aquifer has its upper boundary at the water table, so it is open to the atmosphere and can be recharged directly by water infiltrating from the ground surface. The best description is that this aquifer receives water directly from the ground surface above, reflecting that direct recharge from rainfall and surface water is what fills and sustains it. This contrasts with confined systems, which are capped by an impermeable layer and receive recharge from distant locations, and with aquifers not influenced by rainfall, which would not be recharged from the surface.