What is an aquifer?

• A. A type of rainfall
• B. Water-bearing permeable rock or unconsolidated material that transmits water to springs and wells
• C. A dry soil layer
• D. A device that filters water

Answer: (B)

An aquifer is a layer of rock or sediment that can store and transmit groundwater. It must be permeable enough for water to move through it, and it holds water in the spaces between grains or in fractures. Because of this, aquifers can feed springs and supply water to wells. The water in an aquifer is stored underground and can flow slowly, allowing pumped wells to draw water from it. Some aquifers are unconfined, meaning the water table is open to the surface, while others are confined between impermeable layers and water is under pressure.

Recharge happens when rainfall or surface water infiltrates down to replenish the aquifer. This concept is central to groundwater supplies used for drinking water. In contrast, rainfall itself is entering the surface system, not the underground storage and transmission layer; a dry soil layer doesn’t effectively transmit groundwater to springs or wells; and a device that filters water is a treatment method, not a subsurface water-bearing formation.