What is the level of groundwater known as?

The level of groundwater is referred to as the water table. The water table signifies the upper surface of saturated soil or rock, where the pores are completely filled with water. It serves as a critical boundary distinguishing the zone of saturation, where all openings in the soil or rock are filled with water, from the zone of aeration above, where air occupies some of the pores.

Understanding the water table is vital in various fields such as construction, environmental science, and land management. Knowing the depth and fluctuations of the water table can influence decisions regarding site development, foundation design, and drainage systems, as well as affect local ecosystems.

The other terms provided relate to water but refer to different concepts: an aquifer is a geological formation capable of storing and transmitting water, which can feed into the water table; subsurface refers generally to the area beneath the ground but isn’t specifically about water levels; and waterline, while it could imply a line indicating the level of water, lacks the specificity of the term "water table," which correctly identifies the point at which groundwater pressure is equal to atmospheric pressure.