When dealing with water wells, the underground level from which ground water is extracted is either a layer of permeable rock capable of bearing water or materials such as gravel, silt, clay or sand that are not consolidated. This layer is known as the Aquifer.
Hydrogeology studies aquifers and water flow and also characterizes types of aquifers. The water table is also linked to this layer as it is the surface of saturated material in the aquifer.
