What is the term for the level of water below the soil surface that is saturated?

The term "water table" refers specifically to the upper surface of the zone of saturation in soil or rock, where all the available pore spaces are filled with water. It is a critical concept in hydrology and refers to the actual boundary between the saturated ground below and the unsaturated ground above. Understanding the water table is essential for several practical applications, including agriculture, water management, and environmental conservation, as it affects the availability of groundwater for various uses.

Other options, such as "water reservoir," typically refer to a larger body of water, either naturally occurring or man-made, that stores significant amounts of water, but does not indicate the saturation level of soil directly. "Aquifer level" speaks to specific underground layers that can store and transmit water but is more complex and may not represent the general level of saturation. "Groundwater level" is similar to the water table concept but is a broader term that may not refer explicitly to the boundary of saturation in soil. Therefore, "water table" accurately captures the definition needed and is the most precise answer.