How is the upper boundary of an unconfined aquifer defined?

The definition of the upper boundary of an unconfined aquifer is characterized by the water table. The water table represents the level below which the ground is saturated with water; this boundary is not fixed and can fluctuate depending on various factors such as precipitation, water extraction, and seasonal variations. In an unconfined aquifer, the water table serves as the surface where the pressure of the groundwater is equal to atmospheric pressure, which distinguishes it from confined aquifers that are bounded by impermeable layers above and below. Understanding the significance of the water table is crucial, as it influences groundwater flow and availability, and is a key factor in hydrology and resource management.