Class 15a: Water resources Water supply and demand Modification of waterways Water quality and...
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Class 15a: Water resources
• Water supply and demand
• Modification of waterways
• Water quality and pollution
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Availability of water
• Only 3% of Earth’s water is fresh
• Only 0.003% is available
• Surface water: streams, lakes, etc.
• Groundwater: found in aquifers
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Demand for water
• Since 1950, per capita water use has tripled: why?
• 1 billion people lack safe water
• Depends on climate, population, level of development
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Demand for water
• U.S. individual use: 180 gallons/day
• Lettuce: 6 gallons
• Glass of milk: 48 gallons
• Eggs: 63 gallons each
• Loaf of bread: 145 gallons
• Pound of beef: 8,500 gallons
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Demand for water
Agriculture Industry/energy
Household
World 70% 25% 8%
U.S. 41% 49% 10%
SW U.S. 85%
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Politics of water
• Military tool since 2500 B.C.
• Jordan R., Tigris and Euphrates, Nile, etc.
• “Environmental security”
• Cooperation among riparian nations needed
• Water wars?
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Aral Sea
• Was the world’s fourth largest lake; now 80% gone
• Central Asian desert climate
• Irrigation on Amu Darya, Syr Darya
– Cotton, rice
– Commercial, not subsistence, farming
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Aral Sea
• Increased salinization
• Fishing industry gone
• Salts and dust from dry lakebed
• Rivers slow, contaminated
• Climate even more continental
• “Ten times worse than Chernobyl”
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Ogallala Aquifer
• Equivalent to a Great Lake; 25-100 years left
• Cattle, wheat, corn, cotton (1/5 of U.S. cropland)
• Drinking water for 2 million
• “Groundwater mining”
– Potentially renewable resource
– Used up to 22 times faster than replaced
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Solutions?
• More groundwater (not long-term)
• Diverting rivers (Columbia? Ob?)
• Towing icebergs (expensive)
• Desalination (expensive, energy-intensive)
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Solutions?
• Conservation!
• Est. 65-70% of water is lost (50% in U.S.)
• True pricing
– Less federally subsidized water in West
– More metering (Sacramento)
• More efficient irrigation
• Reclaiming and recycling
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Modification of streams
• Your responsibility!
• Channelization
– What and where
– Downstream, upstream consequences
• Effects of cities, deforestation
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What is water “quality”?
• Depends on the use
• Drinking, swimming, fishing, aquatic life, industry, etc.
• 2000 EPA assessment: 40% of streams, 45% of lakes, 14% of coasts did not meet quality standards
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Water quality and pollution
• Biological or chemical pollutants
– Pathogens, silt, metals, chemicals
• Point sources: specific location
• Non-point sources: dispersed location
– Agriculture, industry, mining, residences
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Agricultural runoff
• 1/2 to 2/3 of stream pollution in U.S.
• Excess fertilizer
– Eutrophication
– Algae blooms, “dead zone”
• Herbicides, pesticides
• Animal wastes (factory farms)
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Industrial/mining runoff
• Metals, arsenic from gold mining
• PCBs from industry
• Mercury from industry, mining
– Concentration in Arctic
– Cultural, health implications
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Clean Water Act (1972)
• Set U.S. water quality standards
• Goal of no discharge by 1985
• Focus on “end of pipe”
– Cheaper to violate?
• Eastern rivers, Great Lakes greatly improved
• Considered a legislative success story