What defines the water table in an unconfined groundwater system?

The water table in an unconfined groundwater system is defined as the surface between the zone of saturation and the zone of aeration. This is where the saturation of groundwater occurs; below this surface, all the spaces in the soil or rock are filled with water, which is referred to as the zone of saturation. Above the water table, in the zone of aeration, the spaces are filled with air. The water table fluctuates based on factors like precipitation, extraction rates, and seasonal changes, acting as the upper limit of groundwater.

The other choices refer to different attributes or concepts related to groundwater. The point where water pressure equals atmospheric pressure is often referred to in the context of piezometric surfaces rather than the water table itself. The depth to which wells can extract water can vary based on the well's design and the local geology, but it does not define the water table. Lastly, the boundary between confined and unconfined aquifers pertains to the overall groundwater systems and their confinement, but it is not synonymous with the water table itself.