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Chapter 14 Groundwater Noteworthy Information
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Factors that affect the amount of groundwater that seeps into the ground: type of rock or soil climate (dry climates, water evaporates) topography (mountainous regions water runs off the rocky slopes) vegetation (slows flow and removes water) land use (pavement does not allow water to enter the ground)
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Factors that affect porosity of rock: particle shape (round vs. angular) sorting (well-sorted vs. poorly-sorted) Factors that affect permeability of rock: particle size (small vs. large) sorting (well-sorted v.s poorly-sorted)
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Distribution of Groundwater Vadose Phreatic
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A rock can have a number of pores that are not connected to each other. (Pumice, Scoria) Zone of Aeration Water Table Zone of Saturation Impermeable Layer
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Factors that determine the water tables distance from the surface: amount of rainfall time between rains season slope of the ground thickness of soil climate human activity
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What is an ordinary well? a well drilled into the permanent water table What is a perched water table? water that collects on an impermeable layer above the water table
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Springs may result from a perched water table Rollie’s Well
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The best aquifers are made of: uncemented sands and gravels, sandstones Magma or cooling pluton is the heat source for geysers, fumaroles, and hot springs 100 F+ (strong sulfur smell) Geothermal gradient is the heat source for most Eastern U.S. warm springs (mild sulfur smell)
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Geyser Eruption Sequence
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Deep Circulation of Groundwater geothermal gradient 10 C/km or 1.5 F/100ft Warm Spring
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What percentage of the drinking water in the United States comes from groundwater? 50 % What problems have humans created for the groundwater supply? Using the groundwater faster than it can be replenished by nature. Polluting the groundwater supply
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Problems that develop due to the over use of groundwater. The water table drops Saltwater intrusions Subsidence How does groundwater become polluted? Pollution is carried by water seeping through the soil.
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Formation of a cone of depression in the water table Discharge exceeds recharge
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Saltwater contamination due to excessive well pumping Wildwood Crest
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List a few examples of groundwater pollutants. Oil from roads Nitrates from soil fertilizers Pesticides applied to plants Farm wastes Sewage from septic tanks
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Well design requires knowledge of local geology
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What is the difference between hard water and soft water? Hard water contains large amounts of dissolved ions from minerals. Soft water contains very few ions from minerals. Why is artesian water generally harder than ordinary groundwater? Artesian water travels farther and may be warmer than ordinary water, so it can dissolve more mineral matter.
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Artesian Well Model
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Hydraulic head and urban water supplies Just like an artesian, saves money
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List some states that have Karst Topography? Alabama, Florida, Tennessee, Indiana, Virginia, Pennsylvania, Georgia, Missouri, South Dakota and Wyoming. What is Karst Topography?
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