Ground Water
<p ><b>Groundwater</b> is <a href="http://en.wikipedia.org/wiki/Water" title="Water" >water</a> located beneath the earth's surface in <a href="http://en.wikipedia.org/wiki/Soil" title="Soil" >soil</a><a href="http://en.wikipedia.org/wiki/Porosity" title="Porosity" >pore</a> spaces and in the <a href="http://en.wikipedia.org/wiki/Fracture" title="Fracture" >fractures</a> of <a href="http://en.wikipedia.org/wiki/Rock_formation" title="Rock formation" class="mw-redirect" >rock formations</a>. A unit of rock or an unconsolidated deposit is called an <a href="http://en.wikipedia.org/wiki/Aquifer" title="Aquifer" >aquifer</a> when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the <a href="http://en.wikipedia.org/wiki/Water_table" title="Water table" >water table</a>. <a href="http://en.wikipedia.org/wiki/Groundwater_recharge" title="Groundwater recharge" >Groundwater is recharged</a> from, and eventually flows to, the surface naturally; natural discharge often occurs at <a href="http://en.wikipedia.org/wiki/Spring(hydrosphere)" title="Spring (hydrosphere)" class="mw-redirect" >springs</a> and <a href="http://en.wikipedia.org/wiki/Seep(hydrology)" title="Seep (hydrology)" >seeps</a>, and can form <a href="http://en.wikipedia.org/wiki/Oasis" title="Oasis" >oases</a> or <a href="http://en.wikipedia.org/wiki/Wetland" title="Wetland" >wetlands</a>. Groundwater is also often withdrawn for <a href="http://en.wikipedia.org/wiki/Agriculture" title="Agriculture" >agricultural</a>, <a href="http://en.wikipedia.org/wiki/City" title="City" >municipal</a> and<a href="http://en.wikipedia.org/wiki/Industry" title="Industry" >industrial</a> use by constructing and operating extraction <a href="http://en.wikipedia.org/wiki/Water_well" title="Water well" >wells</a>. The study of the distribution and movement of groundwater is<a href="http://en.wikipedia.org/wiki/Hydrogeology" title="Hydrogeology" >hydrogeology</a>, also called groundwater <a href="http://en.wikipedia.org/wiki/Hydrology" title="Hydrology" >hydrology</a>.
Typically, groundwater is thought of as liquid water flowing through shallow aquifers, but technically it can also include <a href="http://en.wikipedia.org/wiki/Soil_moisture" title="Soil moisture" class="mw-redirect" >soil moisture</a>, <a href="http://en.wikipedia.org/wiki/Permafrost" title="Permafrost" >permafrost</a> (frozen soil), immobile water in very low permeability <a href="http://en.wikipedia.org/wiki/Bedrock" title="Bedrock" >bedrock</a>, and deep<a href="http://en.wikipedia.org/wiki/Geothermal_(geology)" title="Geothermal (geology)" class="mw-redirect" >geothermal</a> or <a href="http://en.wikipedia.org/wiki/Petroleum_geology" title="Petroleum geology" >oil formation</a> water. </p>
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Groundwater is hypothesized to provide <a href="http://en.wikipedia.org/wiki/Lubrication" title="Lubrication" >lubrication</a> that can possibly influence the movement of <a href="http://en.wikipedia.org/wiki/Fault(geology)" title="Fault (geology)" >faults</a>. It is likely that much of the <a href="http://en.wikipedia.org/wiki/Earth" title="Earth" >Earth</a>'s subsurface contains some water, which may be mixed with other fluids in some instances. Groundwater may not be confined only to the Earth. The formation of some of the <a href="http://en.wikipedia.org/wiki/Hydrology_of_Mars" title="Hydrology of Mars" class="mw-redirect" >landforms</a> observed on <a href="http://en.wikipedia.org/wiki/Mars" title="Mars" >Mars</a> may have been influenced by groundwater. There is also evidence that liquid water may also exist in the subsurface of <a href="http://en.wikipedia.org/wiki/Jupiter" title="Jupiter" >Jupiter</a>'s moon <a href="http://en.wikipedia.org/wiki/Europa(moon)" title="Europa (moon)" >Europa</a>.<sup id="cite_ref-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Groundwater#cite_note-0" >[1]</a></sup></p>