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Published byEugene Elliott Modified over 9 years ago
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Chapter 14-1 Groundwater Pages Geology
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Groundwater Factors that affect the amount of seepage of water into the ground are: Type of rock or soil on the ground where the water falls Climate, topography, land use, vegetation
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Porosity The percent of a materials volume that is pore space – the more the space, the more water that can be held. Depends on: Particle shape More rounded particles allows for more pore spaces Sorting Well sorted material (same size) offers greatest pore spaces
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Permeability The rate at which water or other liquids pass through the pore spaces of a rock. Permeability increases with grain size Ex: sand and gravel is highly permeable while clay and shale has low permeability. So, can a rock be highly porous but not be permeable? – explain… Or, can a nonporous rock become highly permeable?
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The water table The water table is the upper surface of the zone of saturation Above this level up to the surface, the ground can still hold more water, and this area is called the zone of aeration This zone of aeration contains 3 parts:
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The three parts of the zone of aeration are:
1) capillary fringe Found just above the water table, where water rises due to water’s attraction to the soil particles. This is called Capillary action 2) a dry region of soil except after rainfall 3) organic or humus layer just below the surface
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What are some factors that affect the depth of the water table
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How is the water table important?
Seepage from water table keeps streams flowing between rain events Maintains water levels of lakes and wetlands Provides drinking water from natural springs and human-made wells
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Types of wells Ordinary well Water must be pumped out of the well
Artesian well Well water is under some pressure to force the water up the well – does not have to be to the top. Large volumes of water found underground in the pore spaces is called an aquifer. ***best aquifers are those made of uncemented sands and gravel, followed by porous sandstones.
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View of an artesian formation
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How does a geyser occur? Geyser animation
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Conserving Groundwater - Water Budgets
Chapter 14-2 Pages
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Water budget Describes the income and spending of water for a region.
The income is rain or snow The spending includes water loss by use, runoff, and by evapotranspiration. Weather is the controlling factor of evapotranspiration - when temperatures are high, the amount of evapotranspiration would also increase. - the opposite is also true, low temperature causes low evapotranspiration.
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Four parts of a water budget
Recharge When moisture is added to the groundwater, the soil water storage is filling Surplus Occurs when the rainfall is greater than the need for moisture, and the storage water is filled Usage If the need for moisture is greater than the rainfall and the plants draw water from the soil water supply Deficit Occurs when the need for moisture is greater than the rainfall and the soil water is gone.
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Examples of water budget
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Another water budget example
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Water conservation In many regions, water is being used at a faster rate than can be naturally replenished. Pollution is also threatening many groundwater supplies
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Percent water consumption
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Overuse of groundwater
When groundwater supplies are depleted, the water table drops This may cause wells, springs to go dry If this happens along coastal regions, salt water may seep into overused freshwater aquifers and damage water supplies by making them salty and unusable.
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Overuse of groundwater may cause ground levels to drop due to compaction of the removal of groundwater below. Entire valleys may subside like the San Joaquin Valley of California (up to 30 feet drop from )!
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Sinkholes may form from loss of groundwater
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In Florida In Bowling Green, KY
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Groundwater pollution
Groundwater may become polluted by human activities: Fertilizer Oil from roadways Pesticides Sewage from septic tanks and sewers Hazardous wastes from industry Toxic waste dumps (Love Canal – New York)
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Images of Love Canal
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Groundwater and Geology
Chapter 14-3 Pages
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Geologic formations formed by groundwater
Groundwater moving through bedrock may take in dissolved minerals. This water is now called “hard water”. Calcium ions is most common mineral in hard H2O What do we do at home to reduce hard water? Hard water causes water spots, poor washing Artesian water is usually harder than regular groundwater Groundwater is almost always harder than river water
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Mineral deposits When water evaporates or cools, it will leave behind any minerals that were dissolved in the water. Examples: geyserite, geodes, mineral veins of copper, quartz, gold, silver, calcite, etc. Petrified wood is formed when minerals replace decaying wood of buried trees Calcite is most common dissolved mineral cement for grains of sand and pebbles.
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Mineral springs A spring with a high concentration of mineral matter
May be due to: Hot water Water passes through easily dissolved minerals Water contains large quantity of gases Some mineral springs areas have become health resorts – Hot Springs, Arkansas Yellowstone’s Mammoth Hot Springs forms calcium deposits called traventine
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Caverns Formed in areas with limestone bedrock
Limestone is dissolved by carbonic acid found in the groundwater Dripstone Stalactites Stalagmites When they meet, they form columns or pillars Examples include Mammoth Cave in Kentucky, caves of Calumet and Door County, WI, Eagle Cave west of Madison
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Karst Topography Identified by sinkholes, sinkhole ponds, fissures, lost rivers, and underground rivers Created when caverns collapse Forms where bedrock is made of calcite or dolomite Found in south-central Kentucky, Door County, WI
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