What is the name of the underground level that is saturated with water?

The name of the underground level that is saturated with water is referred to as the water table. The water table represents the upper surface of the zone of saturation, where all the spaces in the soil and rock are filled with water. This layer is dynamic, fluctuating with seasonality and precipitation, and is an important concept in hydrology and land development.

Understanding the water table is crucial for various reasons, including its influence on the design and placement of buildings, foundations, and drainage systems. It directly impacts accessibility to groundwater, which is a critical resource for irrigation and drinking water. The other terms, like aquifer, refer to geological formations that can contain or transmit water, while groundwater zone is a broader term that encompasses the area below the water table. Subsoil, on the other hand, typically refers to the layer of soil beneath the topsoil, which may not necessarily be saturated with water.