What is meant by a perched water table?

What is meant by a perched water table?

• A. A sand deposit above a clay deposit, with free water contained in the sand
• B. A groundwater table located below the surface
• C. A water table all around a hilltop
• D. An aquifer under pressure

Answer: (A)

A perched water table is a small, localized saturated zone that sits above a less permeable layer, so groundwater in the upper, more permeable layer is trapped and forms its own shallow water table separate from the deeper main groundwater. This happens when a sand layer lies atop an impermeable layer like clay, preventing water from sinking further and creating free water in the sand at a higher elevation than the main aquifer. The scenario described—sand on top of clay with free water in the sand—illustrates this setup directly, making it a perched water table. The other descriptions refer to the broader groundwater table, a water table around a hilltop, or a confined (pressurized) aquifer, none of which capture the perched, separated-lens concept.

A perched water table is a small, localized saturated zone that sits above a less permeable layer, so groundwater in the upper, more permeable layer is trapped and forms its own shallow water table separate from the deeper main groundwater. This happens when a sand layer lies atop an impermeable layer like clay, preventing water from sinking further and creating free water in the sand at a higher elevation than the main aquifer. The scenario described—sand on top of clay with free water in the sand—illustrates this setup directly, making it a perched water table. The other descriptions refer to the broader groundwater table, a water table around a hilltop, or a confined (pressurized) aquifer, none of which capture the perched, separated-lens concept.