Water Quality 3

Water Quality 3 - Groundwater and Groundwater Quality...

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Groundwater and Groundwater Quality Introduction to groundwater – flow and properties Ch. 7: pp. 264-273 Groundwater quality Ch. 9: pp. 389-393 Lecture notes
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What is Groundwater? It is water stored underground in aquifers, which are layers of sand, silt, clay, or rock that can store, transmit, and yield water via the pores and cracks within the soil/rock. It is not giant underground caves filled with water. 1 ft 3 of loose sand will hold about 2 gallons of water. 1 ft 3 of finely cracked sandstone will hold about 1 quart of water. Groundwater is about 99% ( ES&T , 2010) of all freshwater available on earth, and has been used for 6,000 years. For example, about 4,000 BC, 100-ft deep wells were hand-dug in the Middle East. About 39% of public drinking water the US comes from groundwater. Total groundwater use: 67% irrigation, 20% industrial, 13% domestic. In the western US, GW provides 1/2 of the water. Groundwater use has tripled in the past 40 years. US withdraws about 16 billion gallons of GW each day Global withdrawal of GW is about 600 billion gallons each day Approximately 50% of the US population drinks groundwater .
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An aquifer  is a layer of  porous  water-bearing rock and  glacial deposits that transmits water  lying between the surface of the land and the lowest rock formation (i.e., basement rock - bedrock). Bedrock
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Porosity η = = volume total voids of volume Porosity
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Terminology Unsaturated zone - just below the surface; air and water in the crevices; it is not usable to humans, but plants can draw on it; also called the vadose zone Saturated zone - all the spaces around the soil are filled with water Confining bed , aquitard, aquiclude - impermeable layer that restricts the movement of groundwater Aquifer - saturated layer through which water can flow through easily
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Types of Aquifers and Wells TYPES OF AQUIFERS: perched - confining layer or aquitard in the middle of an unsaturated zone (e.g., clay lenses); water moving downward gets trapped on it forms aquifer unconfined - aquitard below the saturated zone confined aquifer - confining layer above and below the aquifer; this may be under pressure. An Artesian aquifer
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This note was uploaded on 06/03/2011 for the course 53 50 taught by Professor Parkin during the Spring '11 term at University of Iowa.

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Water Quality 3 - Groundwater and Groundwater Quality...

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