perchwatertafel

Perchwatertafel, the Dutch term for perched water table, refers to a localized body of groundwater that is situated above the main regional water table and separated from it by an impermeable or much less permeable layer, such as an aquitard. This term is used in Dutch-language hydrogeology to describe a perched groundwater zone that can form distinct from the larger aquifer system.

A perched water table forms when recharge infiltrates through a permeable layer that overlies an impermeable barrier. The impermeable layer traps water above it, creating a higher hydraulic head than the surrounding regional groundwater. The resulting perched aquifer is typically smaller and shallower than the main aquifer and can have its own flow system.

Characteristics of a perchwatertafel include limited extent, relatively shallow depth, and potential discharge to nearby springs, wetlands, or surface streams. Water quality in perched aquifers can differ from the regional groundwater because of its closer contact with surface materials and the overlaying barrier. Because of their shallow depth and confined volume, perched water tables can be more vulnerable to contamination from surface activities.

Occurrence is common in sedimentary settings with alternating layers, such as sands or gravels overlain by clays or silts. They are frequently found in alluvial fans, glacial outwash plains, or terrace deposits where impermeable layers interrupt deeper groundwater flow.

See also: perched aquifer, groundwater, aquitard, hydrology.