What is the zone of saturation?

• A. A The top of the water table
• B. B The ground area where all pore spaces are filled with water
• C. C A layer of impermeable rock
• D. D The surface water body boundary

Answer: (B)

The zone of saturation is the portion of the subsurface where all pore spaces are filled with water. It lies below the water table, which marks the upper boundary between saturated conditions and the unsaturated zone. In this saturated layer, groundwater occupies every void in soil and rock (including fractures). This is why the zone is defined by complete saturation, not by the surface features or by an impermeable layer. A layer of impermeable rock acts as a barrier or boundary, not the zone itself, and the surface water boundary refers to contact with lakes, rivers, or streams, not to the saturated zone.