What is the water table?

• A. A The interface between groundwater and surface water
• B. B The bottom of the zone of saturation
• C. C The layer above the zone of saturation
• D. D The top of the zone of saturation

Answer: (D)

The water table is the upper boundary of the zone of saturation in the ground. It marks where underground pore spaces switch from being filled with water to containing air. Above this boundary lies the unsaturated (vadose) zone, where both air and water occupy the pores, while below it is the saturated zone where every pore is filled with water. The water table can slope or curve with the terrain and changes with rainfall, recharge, and pumping. It may lie close to the surface in wet areas or during wet seasons, and it can drop during drought or intensive groundwater extraction. While groundwater can interact with surface water (discharging to streams or being recharged by them), the water table itself is specifically the top of the saturated region, not the interface between groundwater and surface water.