What is the area in the ground where most of the pore spaces are filled with air and has some water present?

• A. Zone of Aeration (Vadose) [unsaturated]
• B. Zone of Saturation
• C. Water table
• D. Aquifer

Answer: (A)

This question tests understanding of groundwater zones, specifically the difference between unsaturated and saturated conditions. The region where most pore spaces are filled with air and only some water is present lies above the water table in the unsaturated, or vadose, zone. Water here exists as thin films on soil particles and in small capillary pockets, but air dominates the pore space. Below this boundary, the zone of saturation has all pores filled with water, and the water table marks the top of that saturated zone. An aquifer is a permeable body of rock or sediment that stores and transmits groundwater, not a zone itself. So the area described is the zone of aeration (vadose zone).