chapter13

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Water Resources
Chapter 13
Core Case Study: Water Conflicts in the
Middle East: A Preview of the Future
 Water shortages in the Middle East:
hydrological poverty
 Nile River
 Jordan Basin
 Tigris and Euphrates Rivers
 Peacefully solving the problems
Three Major River Basins in the
Middle East
13-1 Will We Have Enough Usable Water?
 Concept 13-1A We are using available
freshwater unsustainably by wasting it, polluting
it, and charging too little for this irreplaceable
natural resource.
 Concept 13-1B One of every six people does
not have sufficient access to clean water, and
this situation will almost certainly get worse.
Freshwater Is an Irreplaceable Resource
That We Are Managing Poorly (1)
 Why is water so important?
 Earth as a watery world: 71%
 Freshwater availability: 0.024%
 Poorly managed resource
 Hydrologic cycle
 Water pollution
Freshwater Is an Irreplaceable Resource
That We Are Managing Poorly (2)
 Access to water is
•
•
•
•
A global health issue
An economic issue
A women’s and children’s issue
A national and global security issue
Girl Carrying Well Water over Dried Out
Earth during a Severe Drought in India
Most of the Earth’s Freshwater Is Not
Available to Us
 Hydrologic cycle
• Movement of water in the seas, land, and air
• Driven by solar energy and gravity
 People divided into
• Water haves
• Water have-nots
We Get Freshwater from Groundwater
and Surface Water (1)
 Ground water
 Zone of saturation
 Water table
 Aquifers
• Natural recharge
• Lateral recharge
We Get Freshwater from Groundwater
and Surface Water (2)
 Surface Water
• Surface runoff
• Watershed (drainage) basin
• Reliable runoff
• 1/3 of total
Natural Capital: Groundwater System:
Unconfined and Confined Aquifer
Unconfined Aquifer Recharge Area
Evaporation and transpiration Evaporation
Precipitation
Confined
Recharge
Area
Runoff
Flowing
artesian well
Infiltration
Water
table
Well
requiring
a pump
Stream
Lake
Infiltration
Less permeable
material such as
clay
Fig. 13-3, p. 316
We Use a Large and Growing Portion of
the World’s Reliable Runoff
 2/3 of the surface runoff: lost by seasonal floods
 1/3 runoff usable
• Domestic: 10%
• Agriculture: 70%
• Industrial use: 20%
 Fred Pearce, author of When the Rivers Run Dry
Case Study: Freshwater Resources in the
United States
 More than enough renewable freshwater,
unevenly distributed
 Effect of
• Floods
• Pollution
• Drought
 2007: U.S. Geological Survey projection
• Water hotspots
Average Annual Precipitation and Major
Rivers, Water-Deficit Regions in U.S.
Fig. 13-4a, p. 317
Average annual precipitation (centimeters)
Less than 41
81–122
41–81
More than 122
Fig. 13-4a, p. 317
Fig. 13-4b, p. 317
Acute shortage
Shortage
Adequate supply
Metropolitan regions with
population greater than 1 million
Fig. 13-4b, p. 317
Water Hotspots in 17 Western U.S. States
Washington
Montana
Oregon
Idaho
Wyoming
Nevada
North
Dakota
South
Dakota
Nebraska
Utah
Colorado
California
Arizona
New
Mexico
Kansas
Oklahoma
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Fig. 13-5, p. 318
Water Shortages Will Grow (1)
 Dry climate
 Drought
 Too many people using a normal supply of water
Water Shortages Will Grow (2)
 Wasteful use of water
 China and urbanization
 Hydrological poverty
Natural Capital Degradation: Stress on
the World’s Major River Basins
Asia
Europe
North
America
Africa
South
America
Australia
Stress
High
None
Fig. 13-6, p. 319
Long-Term Severe Drought Is Increasing
 Causes
• Extended period of below-normal rainfall
• Diminished groundwater
 Harmful environmental effects
•
•
•
•
•
Dries out soils
Reduces stream flows
Decreases tree growth and biomass
Lowers net primary productivity and crop yields
Shift in biomes
In Water-Short Areas Farmers and Cities
Compete for Water Resources
 2007: National Academy of Science study
• Increased corn production in the U.S. to make
ethanol as an alternative fuel
• Decreasing water supplies
• Aquifer depletion
• Increase in pollution of streams and aquifers
Who Should Own and Manage
Freshwater Resources? (1)
 Most water resources
• Owned by governments
• Managed as publicly owned resources
 Veolia and Suez: French companies
• Buy and manage water resources
• Successful outcomes in many areas
Who Should Own and Manage
Freshwater Resources? (2)
 Bechtel Corporation
• Poor water management in Bolivia
 A subsidiary of Bechtel Corporation
• Poor water management in Ecuador
 Potential problems with full privatization of water
resources
• Financial incentive to sell water; not conserve it
• Poor will still be left out
13-2 Is Extracting Groundwater
the Answer?
 Concept 13-2 Groundwater that is used to
supply cities and grow food is being pumped
from aquifers in some areas faster than it is
renewed by precipitation.
Water Tables Fall When Groundwater Is
Withdrawn Faster Than It Is Replenished
 India, China, and the United States
• Three largest grain producers
• Overpumping aquifers for irrigation of crops
 India and China
• Small farmers drilling tubewells
• Effect on water table
 Saudi Arabia
• Aquifer depletion and irrigation
Trade-Offs: Withdrawing Groundwater,
Advantages and Disadvantages
TRADE-OFFS
Withdrawing Groundwater
Advantages
Disadvantages
Useful for drinking
and irrigation
Aquifer depletion
from overpumping
Available year-round
Sinking of land
(subsidence) from
overpumping
Exists almost
everywhere
Renewable if not
overpumped or
contaminated
No evaporation
losses
Cheaper to extract
than most surface
waters
Aquifers polluted for
decades or centuries
Saltwater intrusion into
drinking water supplies
near coastal areas
Reduced water flows
into surface waters
Increased cost and
contamination from
deeper wells
Fig. 13-7, p. 321
Natural Capital Degradation: Irrigation in
Saudi Arabia Using an Aquifer
Case Study: Aquifer Depletion in the
United States
 Ogallala aquifer: largest known aquifer
• Irrigates the Great Plains
• Water table lowered more than 30m
• Cost of high pumping has eliminated some of the
farmers
• Government subsidies to continue farming
deplete the aquifer further
• Biodiversity threatened in some areas
 California Central Valley: serious water depletion
Natural Capital Degradation: Areas of
Greatest Aquifer Depletion in the U.S.
Groundwater
Overdrafts:
High
Moderate
Minor or none
Fig. 13-9, p. 322
Natural Capital Degradation: The Ogallala
is the World’s Largest Known Aquifer
WYOMING
SOUTH DAKOTA
NEBRASKA
COLORADO
KANSAS
NEW MEXICO
OKLAHOMA
TEXAS
Miles
0
100
160
0
Kilometers
Saturated thickness
of Ogallala Aquifer
Less than 61 meters (200 ft.)
61–183 meters (200–600 ft.)
More than 183 meters (600 ft.)
(as much as 370 meters or 1,200 ft. in places)
Fig. 13-10, p. 323
Groundwater Overpumping Has Other
Harmful Effects (1)
 Limits future food production
 Bigger gap between the rich and the poor
 Land subsidence
• Mexico City
 Sinkholes
Groundwater Overpumping Has Other
Harmful Effects (2)
 Groundwater overdrafts near coastal regions
• Contamination of the groundwater with saltwater
• Undrinkable and unusable for irrigation
Solutions: Groundwater Depletion, Using
Water More Sustainably
SOLUTIONS
Groundwater Depletion
Prevention
Control
Waste less water
Raise price of water
to discourage waste
Subsidize water
conservation
Tax water pumped
from wells near
surface waters
Limit number of wells
Set and enforce
minimum stream flow
levels
Do not grow waterintensive crops in
dry areas
Divert surface water
in wet years to
recharge aquifers
Fig. 13-11, p. 324
Science Focus: Are Deep Aquifers
the Answer?
 Locate the deep aquifers; determine if they
contain freshwater or saline water
 Major concerns
• Geological and ecological impact of pumping
water from them
• Flow beneath more than one country
• Who has rights to it?
Active Figure: Threats to aquifers
13-3 Is Building More Dams the Answer?
 Concept 13-3 Building dam and reservoir
systems has greatly increased water supplies in
some areas, but it has disrupted ecosystems
and displaced people.
Large Dams and Reservoirs Have
Advantages and Disadvantages (1)
 Main goals of a dam and reservoir system
• Capture and store runoff
• Release runoff as needed to control:
•
•
•
•
Floods
Generate electricity
Supply irrigation water
Recreation (reservoirs)
Large Dams and Reservoirs Have
Advantages and Disadvantages (2)
 Advantages
• Increase the reliable runoff available
• Reduce flooding
• Grow crops in arid regions
Large Dams and Reservoirs Have
Advantages and Disadvantages (3)
 Disadvantages
•
•
•
•
•
Displaces people
Flooded regions
Impaired ecological services of rivers
Loss of plant and animal species
Fill up with sediment within 50 years
Advantages and Disadvantages of Large
Dams and Reservoirs
The Ataturk Dam Project in
Eastern Turkey
Some Rivers Are Running Dry and Some
Lakes Are Shrinking
 Dams disrupt the hydrologic cycle
 Major rivers running dry part of the year
•
•
•
•
•
Colorado and Rio Grande, U.S.
Yangtze and Yellow, China
Indus, India
Danube, Europe
Nile River-Lake Victoria, Egypt
 Lake Chad Africa: disappearing
Case Study: The Colorado River Basin—
An Overtapped Resource (1)
 2,300 km through 7 U.S. states
 14 Dams and reservoirs
 Located in a desert area within the rain shadow
of the Rocky Mountains
 Water supplied mostly from snowmelt of the
Rocky Mountains
Case Study: The Colorado River Basin—
An Overtapped Resource (2)
 Supplies water and electricity for more than 25
million people
 Irrigation of crops
 Recreation
Case Study: The Colorado River Basin—
An Overtapped Resource (3)
 Four Major problems
• Colorado River basin has very dry lands
• Modest flow of water for its size
• Legal pacts allocated more water for human use
than it can supply
• Amount of water flowing to the mouth of the river
has dropped
Case Study: The Colorado River Basin—
An Overtapped Resource (4)
 What will happen if some of the reservoirs empty
out?
• Economic and ecological catastrophe
• Political and legal battles over water
The Colorado River Basin
Aerial View of Glen Canyon Dam Across
the Colorado River and Lake Powell
The Flow of the Colorado River Measured
at Its Mouth Has Dropped Sharply
35
30
Hoover Dam
completed (1935)
Flow (billion cubic meters)
25
20
15
Glen Canyon
Dam completed
(1963)
10
5
0
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Year
Fig. 13-16, p. 328
Case Study: China’s Three
Gorges Dam (1)
 World’s largest hydroelectric dam and reservoir
 2 km long across the Yangtze River
 Benefits
• Electricity-producing potential is huge
• Holds back the Yangtze River floodwaters
• Allows cargo-carrying ships
Case Study: China’s Three
Gorges Dam (2)
 Harmful effects
• Displaces about 5.4 million people
• Built over a seismic fault
• Significance?
• Rotting plant and animal matter producing CH4
• Worse than CO2 emissions
• Will the Yangtze River become a sewer?
13-4 Is Transferring Water from One
Place to Another the Answer?
 Concept 13-4 Transferring water from one
place to another has greatly increased water
supplies in some areas, but it has also disrupted
ecosystems.
CA, U.S., Transfers Water from WaterRich Areas to Water-Poor Areas
 Water transferred by
• Tunnels
• Aqueducts
• Underground pipes
 May cause environmental problems
 California Water Project
The California Water Project and the
Central Arizona Project
Sacramento
River
CALIFORNIA
NEVADA
Shasta Lake
Oroville Dam and
Reservoir
UTAH
Feather
Lake Tahoe
River
North Bay
Aqueduct
San Francisco
Sacramento
South Bay
Aqueduct
San Luis Dam
and Reservoir
Fresno
Hoover Dam
and Reservoir
(Lake Mead)
Los Angeles
Aqueduct
California Aqueduct
Colorado River
Aqueduct
Santa Barbara
Los Angeles
San Diego
Salton Sea
Colorado
River
ARIZONA
Central Arizona
Project
Phoenix
Tucson
MEXICO
Fig. 13-17, p. 330
Case Study: The Aral Sea Disaster (1)
 Large-scale water transfers in dry central Asia
 Salinity
 Wetland destruction and wildlife
 Fish extinctions and fishing
Case Study: The Aral Sea Disaster (2)
 Wind-blown salt
 Water pollution
 Climatic changes
 Restoration efforts
Natural Capital Degradation: The Aral
Sea, Shrinking Freshwater Lake
1976
2006
Stepped Art
Fig. 13-18a, p. 331
Ship Stranded in Desert Formed by
Shrinkage of the Aral Sea
China Plans a Massive Transfer of Water
 South-North Water Transfer Project
 Water from three rivers to supply 0.5 billion
people
 Completion in about 2050
 Impact
• Economic
• Health
• Environmental
13-5 Is Converting Salty Seawater to
Freshwater the Answer?
 Concept 13-5 We can convert salty ocean
water to freshwater, but the cost is high, and the
resulting salty brine must be disposed of without
harming aquatic or terrestrial ecosystems.
Removing Salt from Seawater Seems
Promising but Is Costly (1)
 Desalination
• Distillation
• Reverse osmosis, microfiltration
 15,000 plants in 125 countries
• Saudi Arabia: highest number
Removing Salt from Seawater Seems
Promising but Is Costly (2)
 Problems
• High cost and energy footprint
• Keeps down algal growth and kills many marine
organisms
• Large quantity of brine wastes
 Future economics
Science Focus: The Search for Improved
Desalination Technology
 Desalination on offshore ships
• Solar or wind energy
 Better membranes
 Better disposal options for the brine waste
 Reduce water needs, conserve water
13-6 How Can We Use Water More
Sustainably?
 Concept 13-6 We can use water more
sustainably by cutting water waste, raising water
prices, slowing population growth, and
protecting aquifers, forests, and other
ecosystems that store and release water.
Reducing Water Waste Has Many
Benefits (1)
 Water conservation
• Improves irrigation efficiency
• Improves collection efficiency
• Uses less in homes and businesses
Reducing Water Waste Has Many
Benefits (2)
 Worldwide: 65–70% loss
• Evaporation, leaks, etc.
 Water prices: low cost to user
 Government subsidies: more needed?
We Can Cut Water Waste in Irrigation
 Flood irrigation
• Wasteful
 Center pivot, low pressure sprinkler
 Low-energy, precision application sprinklers
 Drip or trickle irrigation, microirrigation
• Costly; less water waste
Major Irrigation Systems
Center pivot
Drip irrigation
(efficiency 90–95%)
(efficiency 80% with low-pressure
sprinkler and 90–95% with LEPA
sprinkler)
Above- or below-ground
(efficiency 60% and 80% with surge valves) pipes or tubes deliver water
to individual plant roots.
Water usually comes from an
aqueduct system or a nearby river.
Gravity flow
Water usually pumped from
underground and sprayed
from mobile boom with
sprinklers.
Fig. 13-20, p. 335
Center pivot
Drip irrigation
(efficiency 90–95%)
(efficiency 80% with low-pressure
sprinkler and 90–95% with LEPA
sprinkler)
Above- or below-ground
(efficiency 60% and 80% with surge valves) pipes or tubes deliver water
to individual plant roots.
Water usually comes from an
aqueduct system or a nearby river.
Gravity flow
Water usually pumped from
underground and sprayed
from mobile boom with
sprinklers.
Stepped Art
Fig. 13-20, p. 335
Solutions: Reducing Irrigation
Water Waste
Developing Countries Use Low-Tech
Methods for Irrigation
 Human-powered treadle pumps
 Harvest and store rainwater
 Create a canopy over crops: reduces
evaporation
 Fog-catcher nets
We Can Cut Water Waste in Industry
and Homes
 Recycle water in industry
 Fix leaks in the plumbing systems
 Use water-thrifty landscaping: xeriscaping
 Use gray water
 Pay-as-you-go water use
Solutions: Reducing Water Waste
We Can Use Less Water to
Remove Wastes
 Can we mimic how nature deals with waste?
 Waterless composting toilets
We Need to Use Water More Sustainably
 “The frog does not drink up the pond in which it
lives”
 Blue revolution
Solutions: Sustainable Water Use
SOLUTIONS
Sustainable Water Use
Waste less water and subsidize
water conservation
Do not deplete aquifers
Preserve water quality
Protect forests, wetlands,
mountain glaciers, watersheds,
and other natural systems that
store and release water
Get agreements among regions
and countries sharing surface
water resources
Raise water prices
Slow population growth
Fig. 13-23, p. 337
What Can You Do? Water Use and Waste
13-7 How Can We Reduce the Threat
of Flooding?
 Concept 13-7 We can lessen the threat of
flooding by protecting more wetlands and natural
vegetation in watersheds and by not building in
areas subject to frequent flooding.
Some Areas Get Too Much Water from
Flooding (1)
 Flood plains
•
•
•
•
Highly productive wetlands
Provide natural flood and erosion control
Maintain high water quality
Recharge groundwater
 Benefits of floodplains
• Fertile soils
• Nearby rivers for use and recreation
• Flatlands for urbanization and farming
Some Areas Get Too Much Water from
Flooding (2)
 Dangers of floodplains and floods
•
•
•
•
Deadly and destructive
Human activities worsen floods
Failing dams and water diversion
Hurricane Katrina and the Gulf Coast
• Removal of coastal wetlands
Natural Capital Degradation: Hillside
Before and After Deforestation
Oxygen
released by
vegetation
Diverse
ecological
habitat
Evapotranspiration
Trees reduce soil
erosion from heavy
rain and wind
Agricultural
land
Tree roots stabilize soil
Vegetation releases water
slowly and reduces flooding
Forested Hillside
Fig. 13-25a, p. 339
Tree plantation
Roads
destabilize
hillsides
Evapotranspiration decreases
Overgrazing accelerates soil
erosion by water and wind
Winds remove
fragile topsoil
Agricultural
land is flooded
and silted up
Gullies and
landslides
Heavy rain erodes topsoil
Silt from erosion fills rivers and reservoirs
Rapid runoff
causes flooding
After Deforestation
Fig. 13-25b, p. 339
Oxygen
released by
vegetation
Diverse
ecological
habitat
Tree plantation
Evapotranspiration
Trees reduce soil
erosion from heavy
rain and wind
Agricultural
land
Tree roots
stabilize soil
Roads
destabilize
hillsides
Evapotranspiration decreases
Overgrazing accelerates soil
erosion by water and wind
Winds remove
fragile topsoil
Agricultural
land is flooded
and silted up
Gullies and
landslides
Heavy rain erodes topsoil
Vegetation releases water
slowly and reduces flooding
Forested Hillside
Silt from erosion fills
rivers and reservoirs
Rapid runoff
causes flooding
After Deforestation
Stepped Art
Fig. 13-25a, p. 339
Case Study: Living Dangerously on
Floodplains in Bangladesh
 Dense population
 Located on coastal floodplain
 Moderate floods maintain fertile soil
 Increased frequency of large floods
 Effects of development in the Himalayan foothills
 Destruction of coastal wetlands
We Can Reduce Flood Risks
 Rely more on nature’s systems
• Wetlands
• Natural vegetation in watersheds
 Rely less on engineering devices
• Dams
• Levees
Solutions: Reducing Flood Damage
SOLUTIONS
Reducing Flood Damage
Prevention
Control
Preserve forests on
watersheds
Straighten and
deepen streams
(channelization)
Preserve and restore
wetlands in floodplains
Tax development on
floodplains
Use floodplains primarily
for recharging aquifers,
sustainable agriculture
and forestry
Build levees or
floodwalls along
streams
Build dams
Fig. 13-26, p. 340
Active Figure: Effects of deforestation
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