Which term refers to the top boundary of the zone of saturation?

• A. Water Table
• B. Zone of Saturation
• C. Aquifers
• D. Virtual Water

Answer: (A)

The boundary between the saturated groundwater zone and the overlying unsaturated region is called the water table. This surface marks the top of the zone of saturation, below which every pore space is filled with water. Above the water table, pores contain air and water in varying amounts—the vadose (unsaturated) zone. The zone of saturation refers to the entire region below that boundary where pores are fully saturated, not the boundary itself. An aquifer is a rock or sediment layer capable of storing and transmitting groundwater, which is related but describes a resource, not the boundary. Virtual water is a concept about the water embedded in products and trade, unrelated to groundwater boundaries. Therefore, the top boundary of the zone of saturation is the water table.