Water Table
# Beneath the surface, many uneven layers of soil, rock and water interact with precipitation and surface water to change groundwater volumes. The uneven layers create underground flows that influence discharge to surface water and distribute and/or re-distribute minerals and contaminants. The water table is the surface at which water pressure is equal to atmospheric pressure. It is depicted on maps as a line across an aquifer.
Piezometric Surface
# A piezometer is a special tool that is used to take measurements within an aquifer. It is submerged within a well beneath the saturated zone, through less porous rock. Many piezometer wells are drilled within a confined aquifer at certain locations. The piezometric surface of water is the level of water within a piezometric well in a confined aquifer. It is depicted on maps as a line between the walls of a well. When several piezometric surface measurements are available, a hydrogeologist can determine recharge and discharge rates and most importantly groundwater-flow direction and rates.
Piezometric Surface vs. Water Table
# Piezometric surfaces can differ from the water table line. Calculations based upon piezometric surface levels in comparison to the water table levels show how groundwater volumes and qualities can change. Seasonal, contaminant or climate influences can be correlated to changes, providing important resource-management information.