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Ground water - water under ground, usuassly below soil level. Upper level is usually polluted and undrinkable.
porosity - volume of space available in a substance. Ground has about 40%.
permeability - ability of a substance to allow water to pass through it.
aquifer (water carrier) porous permeable layer of rock/sediment that yields water.
aquiclude (water stop/shut) layer of earth that will not yield water.
well - hole dug to yield water. Most dug by drill or auger today, in achient times may have been a room sized hole with a descending ramp at the side.
spring - area that has a natural emmissin of water.
unconfined aquifer - water not trapped (easily polluted).
confined aquifer (artesion system) - water trapped between two aquicludes.
Freebie from the text.