An underground region in which all the pores are filled with water is called the ___________

• A. Zone of saturation
• B. Capillary fringe
• C. Zone of aeration
• D. Aquifer

Answer: (A)

Groundwater fills the spaces in soil and rock in distinct zones. The region where every pore is filled with water is the zone of saturation, which sits below the water table—the level where groundwater pressure balances. Above the water table, pores contain air and water in the zone of aeration, with a thin capillary fringe just above the water table where capillary action pulls some water into the pores. An aquifer is a permeable layer that can store and transmit groundwater; it may include saturated portions, but the term describes the geological formation rather than a specific depth. So the underground region where all pores are filled with water is the zone of saturation.