lecture 5 aquifers

lecture 5 aquifers - Aquifers Lecture 5 (Max) Qinhong Hu...

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Aquifers Lecture 5 (Max) Qinhong Hu ydrogeology Hydrogeology (GEOL 4320 and 5328) Fall 2009
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Outline Aquifers Aquifer materials and particle-size distribution ajoraq ifersoftheUnited tates Major aquifers of the United States 2
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Aquifer atin origin; “water”)and om “to Latin origin; aqua (w a t e r) and fer from ferre to bear”; hence an aquifer is a water-bearer lso called groundwater reservoir, water- earing Also called groundwater reservoir, water bearing formation ermeability >10 -2 arcy Permeability >10 darcy A formation, group of formations, or part of a rmation that contains sufficient saturated formation that contains sufficient saturated permeable material to yield significant quantifies of water to wells and springs pg Good aquifer: high porosity + high permeability nconsolidated sands and gravels sandstones Unconsolidated sands and gravels, sandstones, limestones and dolomites, fractured plutonic and metamorphic rocks 3
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Confining Layer (Bed) Aquitard : a layer of low permeability that can store groundwater and also transmit it slowly from one aquifer to another ; sandy clay quiclude saturated but relatively Aquiclude (exclude ): a saturated but relatively impermeable material that does not yield preciable quantities of water to wells; clay appreciable quantities of water to wells; clay Aquifuge (fug itive; avoid): an absolutely impermeable formation neither storing not transmitting water ; solid granite 4
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Some Notes about Aquifers Definition of an aquifer is relative: in areas of clay (permeability of 10 -4 darcy), a silt of 10 -2 darcy might be used to supply water to a small well Leaky confining layer; aquitard; confining layer are interchangeable terms f i i l b i tt l t f Confining layers can be important elements of regional flow systems, and leaky confining layers ti t i i f i t t f t i f t h can transmit significant amounts of water if the cross-sectional area is large 6
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Classes of Aquifers Unconfined aquifer : not bounded above and is the uppermost aquifer. Water has simply infiltrated from the surface and saturated the subsurface material. If people drill a well into an unconfined aquifer, they have to install a pump to push water to the surface. Confined aquifer : an aquifer bounded above d below by units of distinctly lower and below by units of distinctly lower hydraulic conductivity in which the pore ater pressure is greater than atmospheric water pressure is greater than atmospheric pressure. 7
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About Groundwater Table the absence of roundwater ow the water In the absence of groundwater flow, the water table will be flat A sloping water table indicates the groundwater is flowing The water table has the same general shape as the surface topography Groundwater discharge zones are in pographical low spots topographical low spots Groundwater generally flows away from 9 topographical high spots and towards topographical lows
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Two losing streams supplying water to the lake perched lake A perched lake 11
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Perched aquifers are ll n t l t usually not large; most for household use 12
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This note was uploaded on 12/29/2010 for the course GEOL 4320 taught by Professor Maxhu during the Fall '09 term at UT Arlington.

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lecture 5 aquifers - Aquifers Lecture 5 (Max) Qinhong Hu...

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