when the well is dry, we will know the true worth of water
TRANSCRIPT
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¨ “ When the well is dry, we will know the true worth of water.”
¨ Benjamin Franklin
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Chapter 9Water Resources
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Usable Water is Rare
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Fig. 14-2, p. 307
ContinentPercent of world's water resources and population
Asia 60.5%36%
Africa10%
8%Europe
North and Central America 7.3%
South America and Caribbean 6.4%
26%
15%
5%Oceania
11.3%
0.5%
14%
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¨ Aquifers- small spaces found within permeable layers of rock and sediment where water is found.
¨ Unconfined aquifers- an aquifer that is simply porous rock covered by soil.
¨ Confined aquifers- an aquifer surrounded by a layer of impermeable rock or clay.
Groundwater
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¨ Water table- the uppermost level at which the water in an area fully saturates the rock or soil.
¨ Recharge- the input process of water percolating into an aquifer.
¨ Springs- water from an aquifer that naturally percolates up to the surface.
Groundwater
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¨ Cone of depression- an area where there is no longer any groundwater.
Groundwater
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Fig. 14-8, p. 314
Groundwater Overdrafts:High
Moderate
Minor or none
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¨ Saltwater intrusion- when the pumping of fresh water out of a well is faster than the recharge. Near coastal areas this can cause salt water to infiltrate the aquifer.
Groundwater
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Fig. 14-7, p. 313
Trade-OffsWithdrawing Groundwater
Advantages Disadvantages
Useful for drinking and irrigation
Aquifer depletion from overpumping
Available year-round
Sinking of land (subsidence) from overpumping
Exists almost everywhere Polluted aquifers for
decades or centuries
Renewable if not overpumped or contaminated
Saltwater intrusion into drinking water supplies near coastal areas
Reduced water flows into surface waters
No evaporation losses
Cheaper to extract than most surface waters
Increased cost and contamination from deeper wells
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Surface Water
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¨ Productivity in a lake:ú Oligotrophic- low amounts of nutrients
such as phosphorous and nitrogen.ú Mesotrophic- a moderate level of
productivityú Eutrophic- high levels of productivity
Surface Water
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¨ Levees- an enlarged bank built up on each side of the river.
¨ Dikes- similar to a levee but built to prevent ocean waters from flooding adjacent land.
Altering the Availability of Water
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¨ Dams- a barrier that runs across a river or stream to control the flow of water.
¨ Reservoir- the area where water is stored behind the dam.
Altering the Availability of Water
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¨“ Water is life’s mater and matrix, mother and medium. There is no life without water.”
¨ Albert Szent-Gyorgyi
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Fig. 14-13a, p. 317
Provides water for year-round irrigation of cropland
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation
Provides water for drinking Downstream
cropland and estuaries are deprived of nutrient-rich silt
Reservoir is useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Downstream flooding is reduced
Migration and spawning of some fish are disrupted
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¨ Fish ladders- a set of stairs with water flowing over them that have been added to some dams to help migrating fish such as salmon get upstream.
Altering the Availability of Water
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¨ Aqueducts- canals or ditches used to carry water from one location to another.
Altering the Availability of Water
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Fig. 14-14, p. 318
Dam
Aqueduct or canal
Upper Basin
LOWER BASIN
0 100 mi.
0 150 km
Lower BasinUPPER BASIN
IDAHO
WYOMING
Salt Lake City
Grand JunctionDenver
UTAH
NEVADACOLORADOLake
Powell
Las VegasGrand Canyon Glen Canyon
Dam
Boulder CityNEW MEXICO
ARIZONALos Angeles
Albuquerque
PhoenixSan Diego
MexicaliYuma
Tucson
All-American Canal Gulf of
CaliforniaMEXICO
CALIFORNIA
Palm Springs
Colo
rado
Ri
ver
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Fig. 14-16, p. 321
CALIFORNIA
Sacramento River
North Bay Aqueduct
Lake Tahoe
San Francisco Sacramento
South Bay Aqueduct
Hoover Dam and Reservoir (Lake Mead)
NEVADA UTAH
FresnoSan Luis Dam and Reservoir Los Angeles
AqueductColorado River
California Aqueduct
Santa BarbaraColorado River
Aqueduct Central Arizona Project
ARIZONA
Los Angeles
Salton Sea PhoenixSan Diego
Tucson
MEXICO
San Joaquin Valley
Feather River
Shasta LakeOroville Dam and
Reservoir
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¨ Desalination- removing the salt from salt water to obtain fresh water.
Altering the Availability of Water
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¨ Agriculture- the largest user of water around the world.
Agriculture, Industry and Household Needs
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¨ Irrigation techniques-ú Furrow irrigation- a trench that is flooded with
water.ú Flood irrigation- the entire field is flooded with
water.ú Spray irrigation- an apparatus that sprays water
across a field.ú Drip irrigation- using a slow dripping hose that is
laid on or buried beneath the soil.ú Hydroponic agriculture- crops grown in fertilized
water and no soil.
Agriculture, Industry and Household Needs
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Hydroponics
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Aquaponics
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Future Farming?
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Case Study: The Aral Sea Disaster
Ø The Aral Sea was once the world’s fourth largest freshwater lake.
Figure 14-17Monday, May 16, 16
¨ Industry- the second largest user of water worldwide.
Agriculture, Industry and Household Needs
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¨ Households- the third largest user of water worldwide .
Agriculture, Industry and Household Needs
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¨ Water ownership- people can have rights to water use, but they do not own the water.
¨ Water conservation- using techniques such as more efficient water fixtures, faucets and washing machines.
The Future of Water Availability
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Fig. 14-5, p. 310
Wash.
MontanaOregon
N.D.
IdahoWyoming S.D.
Nevada Neb.
UtahColo. Kansas
California Oak.
N.M. Texas
Highly likely conflict potential
Moderate conflict potentialUnmet rural water needs
Substantial conflict potential
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