Aquifer
Aquifer
An aquifer is a geologic formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to springs and wells. Use of the term is often restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people's uses.
Formation of Aquifers
Aquifers are underground layers of porous rock or sand that allows the movement of water between layers of non-porous rock (sandstone, gravel, or fractured limestone or granite). Many people tend to think of aquifers as “underground lakes” which is not the case because water is held between rock particles. Water infiltrates into the soil through pores, cracks, and other spaces until it reaches the zone of saturation where all of the spaces are filled with water (rather than air). The zone of saturation occurs because water infiltrating the soil reaches an impermeable layer of rocks so that it is not able to penetrate any further into the earth (this impermeable layer is known as an “aquitard” or “aquiclude”). Water held in aquifers is know as groundwater.
The top of the zone of saturation is known as the water table. The water table typically follows the form of the above ground topography. The depth of the water table is typically greater inregions with low rainfall than in regions with high rainfall. The water table can rise in wet years and fall in dry years.
Time in Riyadh 
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