Definition: An underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well.
Definition: subterranean zone in which all interstices are filled with water that has a hydraulic head greater than atmospheric pressure due to the weight of overlying groundwater.
Definition: A habitat that is in or on a body of water containing low concentrations of dissolved salts and other total dissolved solids (<0.5 grams dissolved salts per litre).