What does the term "water table" refer to?

The term "water table" refers to the boundary between the unsaturated zone, where soil and rock contain both air and water, and the saturated zone, where all the spaces in the soil and rock are filled with water. This boundary is crucial for understanding groundwater availability, as it marks the upper limit of groundwater. The position of the water table can fluctuate with rainfall, drought, and human activities, making it an essential concept in hydrology, agriculture, and environmental science.

The other options propose variations of water-related concepts but do not accurately define the water table. The saturated zone between soil layers refers more to the area below the water table rather than the boundary itself. The depth at which water can be stored is a broader and less specific description, and the level of groundwater in urban areas could vary significantly depending on numerous factors, but it doesn't specifically describe the water table as a concept.