GroundwaterGroundwater(orground water) is thewaterpresent beneathEarth's surface in soil porespaces and in thefracturesofrock formations.Water in the soil mantle is called subsurface water and is considered in two zones: 1. aturated zone !. "eration zone#orms of ubsurface Water"lso known as groundwater zone.$s the space in which all the pores of the soil are %lled with water.&he water table forms is upper limit and marks a free surfaceaturated 'oneoil pores are onl( partiall( saturated with water.&he space between the land surface and the water table marks the e)tend of this zone.&he zone of aeration has three subzones.'one of "eration&his lies close to the *round surface in the ma+or root band of the ,e*etation from which water is lost to the atmosphere b( e,apotranspiration.oil Water 'one$n this the water is held b( capillar( action.&his zone e)tends from the water table upwards to the limit of the capillar( rise.-apillar( #rin*e&his lies between the soil water zone and the capillar( frin*e.&he thickness of the zone of aeration and its constituent subzones depend upon the soil te)ture and moisture content and ,ar( from re*ion to re*ion.$ntermediate 'oneaturated formations are classi%ed into four cate*ories: 1. ".uifer !. ".uitard /. ".uiclude 0. ".uifu*eaturated #ormation"n a.uifer is a saturated formation of earth material which not onl( stores water but (ields it in su1cient .uantit(.".uifer transmits water relati,el( easil( due to its hi*h permeabilit(.".uifer$t is a formation throu*h which onl( seepa*e is possible and thus the (ield is insi*ni%cant compared to an a.uifer.$t is partl( permeable.".uitard$t is *eolo*ical formation which is essentiall( impermeable to the 2ow of water.$t ma( be considered as closed to water mo,ement e,en thou*h it contain lar*e amounts of water due to its hi*h porosit(.".uiclude$t is a *eolo*ical formation which is neither porous nor permeable.&here are no interconnected openin*s and hence it cannot transmit water".uifu*eUnconfned Aquifer 3 also known as water table aquifer. 4ne in which a free water surface in e)ample a water tables e)ists.Confned Aquifer 3 also known as artesian aquifer5 is an a.uifer which is con%ned between two imper,ious beds such as a.uicludes or a.uifu*es. $s called a leaky aquifer if either both of its con%nin* beds are a.uitards-on%ned and 6ncon%ned ".uifer" water table is the free water surface in an uncon%ned a.uifer.$f the water table intersects the land surface the *roundwater comes out to the surface in the form of sprin*s or seepa*e.Water &ableometimes a lens or localized patch of imper,ious stratum can occur inside an uncon%ned a.uifer in such a wa( that it retains a water table abo,e the *eneral water table.uch a water table retained around the imper,ious material is known as perched water table.7erched Water &able&he position of the water relati,e to the water le,el in a stream determines whether the stream contributes water to the *roundwater stora*e or the other wa( about.7osition of the Water &abletreams which recei,e *roundwater 2ow are called efuent streams.treams which contribute to the *roundwater are known as infuent streams.7osition of the Water &able7orosit( 3 the amount of pore space per unit ,olume of the a.uifer material. $t is e)pressed as where: n8 porosit( 8 ,olume of ,oids8 ,olume of the porous medium ".uifer 7ropertiespeci%c 9ield 3 &he actual ,olume of water that can be e)tracted b( the force of *ra,it( from a unit ,olume of a.uifer material is known as the speci%c (ield5 . &he fraction of water held back in the a.uifer is known as speci%c retention5 . &hus porosit( Formation Porosity, % Specifc yield, %-la( 0:;:: 1;1