Which statement best describes the Zone of Saturation?

• A. All pore spaces are filled with water
• B. Air occupies most pore spaces
• C. It is the upper part of the soil above the water table
• D. It is the layer of soil that holds air

Answer: (A)

The Zone of Saturation is the portion of the subsurface where every pore space is filled with water, and it lies below the water table. The water table marks the boundary where pore pressures become atmospheric; above it, the pore spaces are not completely filled with water, containing air as well. So the essence is that all voids are water-filled, which is why the statement describing all pore spaces as filled with water is the best description. The other ideas describe the region above the water table, where air and water coexist (the unsaturated zone), or simply a layer that holds air, which does not define the saturated zone.