Class 15a: Water resources
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Transcript of Class 15a: Water resources
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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