Transcript Document

Water Resources
Chapter 13
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.
WATER’S IMPORTANCE, AVAILABILITY,
AND RENEWAL
 Water keeps us alive, moderates climate,
sculpts the land, removes and dilutes wastes
and pollutants, and moves continually through
the hydrologic cycle.
 Only about 0.02% of the earth’s water supply is
available to us as liquid freshwater.
Girl Carrying Well Water over Dried Out
Earth during a Severe Drought in India
WATER’S IMPORTANCE, AVAILABILITY,
AND RENEWAL
 Comparison of
population sizes and
shares of the world’s
freshwater among the
continents.
WATER’S IMPORTANCE, AVAILABILITY,
AND RENEWAL
 Some precipitation infiltrates the ground and is
stored in soil and rock (groundwater).
 Water that does not sink into the ground or
evaporate into the air runs off (surface runoff)
into bodies of water.
• The land from which the surface water drains into
a body of water is called its watershed or
drainage basin.
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
WATER’S IMPORTANCE, AVAILABILITY,
AND RENEWAL
 We currently use more than half of the world’s
reliable runoff of surface water and could be
using 70-90% by 2025.
 About 70% of the water we withdraw from rivers,
lakes, and aquifers is not returned to these
sources.
 Irrigation is the biggest user of water (70%),
followed by industries (20%) and cities and
residences (10%).
Average Annual Precipitation and Major
Rivers, Water-Deficit Regions in U.S.
Fig 13-4
Water Hot Spots
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
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
Case Study: Who Should Own and Manage
Freshwater Resources
 There is controversy over whether water
supplies should be owned and managed by
governments or by private corporations.
 European-based water companies aim to control
70% of the U.S. water supply by buying up water
companies and entering into agreements with
cities to manage water supplies.
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.
Other Effects of Groundwater Overpumping
 Groundwater
overpumping can
cause land to sink,
and contaminate
freshwater aquifers
near coastal areas
with saltwater.
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
Natural Capital Degradation: Areas of
Greatest Aquifer Depletion in the U.S.
Fig 13-9
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
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
Fig 13-12
Matilija Dam Removal Project
Click for report
The Colorado River Basin
Fig 13-14
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
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
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 (18 large
power plants)
• 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.
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
Natural Capital Degradation: The Aral
Sea, Shrinking Freshwater Lake
1976
2006
Oxnard water suppliers
United Water
Calleguas Municipal
City of Oxnard
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
Click for link to Desal Response Group
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
Click for Oxnard’s GREAT RO plant info
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
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
Fig 13-21
Solutions: Reducing Water Waste
Fig 13-22
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
How can you save water at home?
Click for Family Water Audit
What Can You Do? Water Use and Waste
Fig 13-24
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
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•
•
•
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
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•
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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 13-25
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