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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
Fig. 13-3, p. 316
Unconfined Aquifer Recharge Area
Precipitation Evaporation and transpiration Evaporation
Confined Recharge Area Runoff
Flowing artesian well
Well requiring a pump Stream
InfiltrationWater table Lake
InfiltrationUnconfined aquiferLess permeable
material such as clay
Confined aquiferConfining impermeable rock layer
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
Fig. 13-4a, p. 317
Average annual precipitation (centimeters)
41–81 More than 122
Less than 41 81–122
Fig. 13-4b, p. 317
Fig. 13-4b, p. 317
Shortage
Acute shortage
Adequate supply
Metropolitan regions with population greater than 1 million
Water Hotspots in 17 Western U.S. States
Fig. 13-5, p. 318
Substantial conflict potential
Highly likely conflict potential
Unmet rural water needs
Moderate conflict potential
Washington
Oregon
MontanaNorth Dakota
Idaho South DakotaWyoming
Nevada NebraskaUtah
ColoradoKansas
CaliforniaOklahoma
New Mexico
Texas
Arizona
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
Fig. 13-6, p. 319
Europe Asia
North America
Africa
South America Australia
Stress
High None
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
Fig. 13-7, p. 321
TRADE-OFFS
Withdrawing Groundwater
Advantages DisadvantagesUseful for drinking and irrigation
Aquifer depletion from overpumping
Available year-roundSinking of land (subsidence) from overpumping
Exists almost everywhere
Aquifers polluted for decades or centuries
Renewable if not overpumped or contaminated
Saltwater intrusion into drinking water supplies near coastal areas
No evaporation losses
Reduced water flows into surface waters
Cheaper to extract than most surface waters
Increased cost and contamination from deeper wells
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.
Fig. 13-9, p. 322
Groundwater Overdrafts:
Moderate
Minor or none
High
Natural Capital Degradation: The Ogallala is the World’s Largest Known Aquifer
Fig. 13-10, p. 323
WYOMINGSOUTH DAKOTA
NEBRASKA
COLORADOKANSAS
OKLAHOMANEW MEXICO
Miles
0
100TEXAS
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)
0
160Kilometers
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
Fig. 13-11, p. 324
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 water-intensive crops in dry areas
Divert surface water in wet years to recharge aquifers
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
Fig. 13-16, p. 328
35
30 Hoover Dam completed (1935)
25
20
15 Glen Canyon Dam completed (1963)
10
Flo
w (
bil
lio
n c
ub
ic m
eter
s)
5
0
1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
Year
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 Water-Rich 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
Fig. 13-17, p. 330
CALIFORNIAShasta Lake NEVADA
Sacramento River
UTAH
North Bay Aqueduct
Feather River
Lake Tahoe
San FranciscoSacramento
South Bay Aqueduct
Hoover Dam and Reservoir (Lake Mead)
Los Angeles Aqueduct
Colorado River
California AqueductColorado River
Aqueduct Central Arizona Project
ARIZONA
Fresno
Santa Barbara
Los Angeles
San DiegoSalton Sea
Phoenix
Tucson
MEXICO
San Luis Dam and Reservoir
San Joaquin V
alley
Oroville Dam and Reservoir
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
Fig. 13-18a, p. 331
Stepped Art
1976 2006
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
Fig. 13-20, p. 335
Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA
sprinkler)Drip irrigation
(efficiency 90–95%)
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
Gravity flow (efficiency 60% and 80% with surge valves)
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Water usually comes from an aqueduct system or a nearby river.
Fig. 13-20, p. 335
Stepped Art
Gravity flow (efficiency 60% and 80% with surge valves)
Water usually comes from an aqueduct system or a nearby river.
Drip irrigation (efficiency 90–95%)
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA
sprinkler)
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
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
Fig. 13-23, p. 337
SOLUTIONS
Sustainable Water Use
Waste less water and subsidize water conservation
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
Do not deplete aquifers
Slow population growth
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
Fig. 13-25a, p. 339
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. 13-25b, 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. 13-25a, p. 339
Oxygen released by vegetation
Diverse ecological habitat Evapotranspiration
Trees reduce soil erosion from heavy rain and wind
Tree roots stabilize soil
Vegetation releases water slowly and reduces flooding
Forested Hillside
Agricultural land
Stepped Art
Tree plantation
Roads destabilize hillsides
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
Evapotranspiration decreases
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
Fig. 13-26, p. 340
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
Build levees or floodwalls along streams
Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry
Build dams
Active Figure: Effects of deforestation
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