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Ch 9 – Water Resources These lectures contain copyrighted images that are provided in the teacher materials for Friedland/Relyea Environmental Science for AP Textbook. By using these lectures, you guarantee that you have legal access to these images or that you have replaced the copyrighted images with images that you have the rights to use.
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If all the water in the world could fit in a two liter bottle, all of the freshwater in the world would fit in a teaspoon
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Available Water
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Water residence time by Reservoir
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Evaporation and transpiration
Groundwater Evaporation and transpiration Evaporation Stream Infiltration Water table Unconfined aquifer Confined aquifer Lake Well requiring a pump Flowing artesian well Runoff Precipitation Confined Recharge Area Aquifer Less permeable material such as clay Confirming permeable rock layer
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Groundwater Precipitation infiltrates and percolates through pores and fractures in soil and rock until it hits an impermeable layer Zone of saturation is at a depth were ground is filled with water Top of this zone is water table Falls in dry weather Rises in wet weather Groundwater flows slowly based on the amount of recharge and the amount of discharge Over pumping of groundwater can result in a variety of environmental problems
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Cone of Depression In an unconfined aquifer, there is an actual depression of the water levels (water table drops). In confined (artesian) aquifers, the cone of depression is a reduction in the pressure head surrounding the pumped well.
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Aquifer Subsidence a gradual sinking of land with respect to its previous level as a result of groundwater being pumped. Cracks and fissures can appear in the land as sinking may not be uniform. Subsidence is virtually an irreversible process.
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Salt Water Intrusion Over pumping of freshwater near salt water results in the movement of the salt water aquifer inward Creates brackish water that is unsuitable for drinking and irrigation Solution: injection well that pumps freshwater into the aquifer pushing the salt water out
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What activity uses the most water?
Use of Fresh Water - US What activity uses the most water? Industrial use Household use Agriculture Power plants
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US water usage by State
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Hidden Water If you want to know more:
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Desalination Removal of salts from ocean water
distillation Reverse osmosis Common in the Middle East Performed by the US to meet water standards for water flowing into Mexico Currently very expensive
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Where does all that salt go?
Salt is in the form of brine water (very salty water that is dense and sinks) Can be put back into the ocean, but Must meet salinity requirements Can impact benthic organisms
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Droughts Effects Causes
Lack of water for farming, household use, industry etc Soil loss, erosion, dust storms Food shortages famines death higher food prices Loss of habitat/biodiversity Economic losses, recession, depression Water conflicts, territory disputes, wars Causes Climate, weather patterns (low rainfall, high temperatures), less snowfall leading to less snowmelt, overusing water during normal rainfall (less storage = less water in reserve) Exacerbated by: Water diversion River channelization Overpumping of groundwater Dams and aqueducts Conversion of native vegetation to rangeland, farmland or urban areas
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Floods Causes Heavy rains, rapidly melting snow, lack of water storage areas Exacerbated by Living in a floodplain Loss of wetlands Dams and aqueducts Native vegetation loss/root loss due to fires, overgrazing, farming, urbanization, mining, etc Impermeable surfaces Loss of top soil, erosion Prolonged droughts Soil compaction, waterlogged soils Effects Water bodies overflow their boundaries and flood surrounding areas Property damage, loss of life Loss of crops increased food prices famines Erosion, loss of top soil Damage to wetlands and other areas that can prevent further storm damage Surface water contamination (sedimenst, sewage, chemicals, etc) Drinking water contamination (sewage, chemicals, etc)
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Media Farming and Flooding: Xeriscaping: Hurricane Katrina New Orleans Hurricane Risk: Hurricane Katrina: Wetland Destruction: Article on CO flooding: Ways to conserve water interactive:
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