(L19)Ground_Water_and_Karstic_Areas_E10

(L19)Ground_Water_an - 1 Ground Water and Karstic Areas GLY 2010 – Summer 2010 Lecture 19 2 Ground Water • Ground Water is found beneath the

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Unformatted text preview: 1 Ground Water and Karstic Areas GLY 2010 – Summer 2010 Lecture 19 2 Ground Water • Ground Water is found beneath the earth’s surface • It is found in two different zones: Vadose Zone Water Table Phreatic Zone • Gravity carries water from the surface downward 3 Vadose Zone - Zone of Aeration • Some is used by plants • Some evaporates • Some is absorbed by soil particles • The remainder continues past the water table • In this zone, much of the available pore space is filled with air - Only a fraction is occupied by water 4 Water Table Formation 4 5 Water Table Fluctuations • Water table follows the contour of the surface above it, but the water table is not confined to being below the ground 6 Phreatic Zone - Zone of Saturation • In this zone, all available pore spaces are filled with water • This zone extends downward from the water table for some distance, generally less than a kilometer, because bedrock below this depth contains no pore spaces in most cases 7 Icebergs As a Source of Water • Although thought is being given to using icebergs as a source of water, there are problems, including danger in shipping lanes, and potential climate change Iceberg Calving in Antarctica 8 Porosity • The relative volume of pore (empty) space in a rock or sediment • It determines how much water the rock or soil can hold White spaces are “pore” (empty) spaces 9 Porosity • Primary porosity in rocks is the pore space that develops when the rocks form Examples include the space between grains in lithified clastic rocks, or vesicles in extrusive igneous rocks • Secondary porosity develops after the rock forms, as the result of fracturing or dissolution 10 10 Porosity Types 11 11 Permeability • The ability of a rock or sediment to allow a fluid (water) to flow through it • Permeability is greatly influenced by the connectiveness of the pore spaces 12 12 Aquifer • An aquifer is a layer(s) of rock or sediment from which fresh water may be obtained in quantity • The word comes from the Latin for “to bear water” • The best aquifers are porous and permeable, with adequate recharge 13 Use of Aquifers • Modern agricultural methods put heavy demands on water systems to supply the water needed to grow food and other crops 13 14 14 Unconfined Aquifers • No impermeable layer above them • They are subject to rapid recharge from above, but may also be easily contaminated by spills, especially if they are shallow • Most water supplies come from unconfined aquifers 15 15 Ogallala Aquifer • The Ogallala Aquifer underlies approximately 225,000 square miles • A major unconfined aquifer 16 16 Aquiclude • Impermeable layers which prevent or greatly slow the flow of a fluid • Clay layers are often aquicludes • Artificial clay layers are used to line landfills, so that water from the landfill won’t leach into the aquifer 17...
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This note was uploaded on 07/13/2011 for the course GLY 2010 taught by Professor Warburton during the Summer '07 term at FAU.

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(L19)Ground_Water_an - 1 Ground Water and Karstic Areas GLY 2010 – Summer 2010 Lecture 19 2 Ground Water • Ground Water is found beneath the

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