potentiometric surface (piezometric surface) A hypothetical surface defined by the level to which water in a confined aquifer rises in observation boreholes. In practice, the potentiometric surface is mapped by interpolation between borehole measurements. As with the water-table in an unconfined aquifer, the slope of the potentiometric surface defines the hydraulic gradient and the horizontal direction of groundwater flow. See HYDRAULIC HEAD.

potentiometric surface(piezometric surface) A hypothetical surface defined by the level to which water in a confined aquifer rises in observation boreholes. In practice, the potentiometric surface is mapped by interpolation between bore-hole measurements. As with the watertable in an unconfined aquifer, the slope of the potentiometric surface defines the hydraulic gradient and the horizontal direction of groundwater flow. See hydraulic head.