gground water

1- Ground water
• It is water that exists beneath the earth s surface in underground streams and aquifers.
• It is found that underground where part/entire حيث الفراغات تكون بشكل جزئي او كليvoid spaces between particles of rock and soil, or in crevices and cracks in rock are filled with water.

• Groundwater an important part of the hydrologic cycle
? Some of the water from melting snow/rainfall seeps into the soil and percolates into the saturated zone to become
Groundwater recharge.
? Eventually, groundwater reappears above the ground into streams, rivers, marshes, lakes and oceans or as springs and flowing wells discharge.
* Groundwater can be characterized according to its vertical distribution.
* Zone of aeration: consists of interstices فجوات occupied partially by water and partially by air.
? Soil water zone : extending from ground surface down through the major root zone
? Vadose zone : extending from lower edge of soil water zone to the upper limit of capillary zone
? Capillary zone: extending from the water table up to the limit of capillary rise.
* Zone of saturation: all interstices are filled with water under hydrostatic pressure.
3- Aquifer

? A formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.
? Type of aquifers
? Confined aquifer (artesian aquifer) ?groundwater is confined by a relatively impermeable stratum, or confined unit, and water is under pressure greater than atmosphere ?artesian wells or flowing wells.
? Unconfined aquifer (water table aquifer) ?an aquifer in which the water table forms the upper boundary ?the water level in a well tapping an unconfined aquifer will rise only to the level of the water table within the aquifer.
? Perched aquifer : perched water الماء الجاثم او الساكن table, an example where an unconfined water body sits on top of a clay lens, separated from the main aquifer : formed perched aquifer