Groundwater Layers

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Aquifer confined/unconfined [Image: visaplan GmbH]

In groundwater layers, the first aquifer is always an unconfined aquifer, whereas all other aquifers are normally confined aquifers.

Whereas the pressure conditions in unconfined aquifers are determined by the free hydrostatic pressure, and the flow velocity is subject to the hydraulic gradient, the situation is different for confined aquifers.

There, the groundwater is under a higher pressure and, as a result of that higher pressure, the flow velocities are also distinctively higher.