An Inverted or Perched water table is a water table that is above the main or regional water table in an unconfined aquifer. The perched water table is generally above a layer of low permeability material such as clay. In the image below, notice that there is an "inverted" water table along bottom of the perched water table.


To amplify on Gary's answer for the situation under a stream: Surface water will be connected to an unconfined groundwater aquifer if the sediments are saturated between the aquifer and the stream. If the head (the elevation of the water i.e. its pressure) is lower at the stream than the adjacent sediments, then it will be a "gaining stream" the water in the ...

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