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Water Chapters 13, 8, & 20
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Water Covers 71% of Earth’s surface
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Water’s Importance Regulates climate Dilutes waste
Sculpts Earth’s surface Major habitat
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Water Supply 97% salt 3% fresh 2.976% in ice caps 0.024% available
Groundwater, lakes, & rivers
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Access to Water Supply Women and children’s issue Global health issue
Economic issue National security issue
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Hydrologic Cycle Natural recycling and purification
Driven by solar energy and gravity
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Human Affects on Hydrological Cycle
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Water Supply: Groundwater
Zone of Saturation Space in soil filled with water Water Table Top of zone of saturation Aquifers Natural recharge Lateral recharge
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Water Supply: Surface Water
Water flows across the earth’s surface Sources: precipitation & snow melt Watershed (drainage basin) Land from where water drains into a particular waterway
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Case Study: US Freshwater Resources
More than enough freshwater but… Unevenly distributed Polluted Droughts
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Case Study: US Freshwater Resources
Water hotspots Identified areas where competition for water may cause conflicts
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Case Study: US Freshwater Resources
Storages will grow due to: Dry climate Droughts Population increases Wasteful use
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Case Study: The Colorado River Basin
Spans 7 states 14 dams & reservoirs Supplied from snow melt of Rockies
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Case Study: The Colorado River Basin
Many uses include: Drinking water Electricity Crop irrigation Recreation ~30 million people Las Vegas Los Angeles San Diego
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Case Study: The Colorado River Basin
Major Problems: Colorado basin has dry lands Modest flow for size Legal pacts allocate for more water for human use than it can supply Amount of water reaching the mouth (Gulf of California) has dropped since 1960
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How can we increase our water supply?
Groundwater
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Groundwater Most are renewable
Provides drinking water for half the world Most are renewable
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US Groundwater Supplies: Withdrawn at 4 times the replacement level
Almost all rural drinking water 1/5 of urban water 37% irrigation Withdrawn at 4 times the replacement level
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High Moderate Minor or none
Groundwater Overdrafts: High Moderate Fig a, p. 308 Minor or none
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Case Study: Ogallala Aquifer
Largest known aquifer Spans 8 states Irrigates the Great Plains Slow recharge = dropping water table Supplies springs – vital habitats
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Case Study: California Central Valley
Serious aquifer depletion Supplies ½ the country’s fruits & veggies
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How can we increase our water supply?
Groundwater Dams & reservoirs
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Main goal of Dams Capture & store runoff Release runoff:
Control floods Generate electricity Supply irrigation Recreation
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Three Gorges Dam Yangtze River, China World’s largest power station
Video in picture
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How can we increase our water supply?
Groundwater Dams & reserviors Desalination
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Desalination Removal of salt from ocean water Processes:
Distillation (evaporate & condensate) Reverse osmosis (microfilter) Middle east the most; US #4
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Desalination Problems: Expensive Large amounts of energy
Disrupts marine ecosystems Brine waste
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Ways that Humans Use Water
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Ways that Humans Use Water
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Ways that Humans Use Water
70% is used for agriculture 1/3rd of US water – irrigation
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Ways that Humans Use Water
70% is used for agriculture 20% industry Electricity generation Cooling machinery Refining metals/paper
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Ways that Humans Use Water
70% is used for agriculture 20% industry 10% household uses
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Water Conservation Estimated 2/3rds of water wasted Why? Low cost
Lack of government incentives
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Irrigation Conservation
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Household Conservation
Fix leaks Landscape smart Water efficient appliances Recycle greywater
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