Transcript Document

Chapter 15 Water Resources
G. Tyler Miller’s
Living in the Environment
14th Edition
Chapter 15
Chapter 15 Key Concepts
 The physical properties of water
 Availability of fresh water
 Methods of increasing freshwater supplies
 Using water more efficiently
 Problems associated with flooding
Sections 1 and 2 Key Ideas
•
•
•
•
•
•
Why is water so important?
What makes water unique?
How much fresh water is available to humans?
What are some of the sources of fresh water?
How do we use the world’s fresh water?
What are some water resource issues faced in
the United States?
Water’s Importance
• No species can live without
water.
• Plays a key role in shaping
the earth’s surface,
moderating climate,
removing and diluting
wastes.
• Takes huge amount to
provide food, shelter and
other needs.
• 71% of our planet
Water’s Unique Properties
 Hydrogen bonding: water’s unique
properties comes from the strong
attractive forces between molecules.
Water’s Unique Properties
 Liquid over wide
temperature range:
without its high boiling
point the oceans would
have evaporated long
ago.
 Changes temperature
slowly: high specific
heat means slow
temperature changes.
Helps moderate
climate.
Water’s Unique Properties
• High heat of evaporation:
evaporation takes a lot of
heat. This explains why
sweating makes you feel
cooler.
• Great dissolving power:
known as the universal
solvent because so may
things dissolve well in it.
Leads to pollution
problems as well.
Water’s Unique Properties
• Filters out ultraviolet
radiation: protecting
aquatic organisms from
sun’ rays.
• Adhesion and cohesion:
strong forces of attraction
between molecules allows
water to rise up inside
plants from roots to
leaves.
Water’s Unique Properties
• Expands when it freezes:
most substances contract
when frozen, not water.
Water expands and is less
dense in its solid form.
Hence, ice floats.
• Water is also one of few
substances found
commonly as a solid,
liquid and gas.
How Much Water Is Available?
• 71% of earth is water
• 97.4% of that is in oceans
• Most of the remaining
2.6% is in ice caps and
glaciers.
• Only about 0.014% is
easily available fresh water.
If earth’s water was 26
gallons, 2.5 teaspoons
would be available.
Supply of Water
Supply of Water Resources
Freshwater
Readily accessible freshwater
Groundwater
0.592%
Biota
0.0001%
Lakes
0.0007%
Ice caps
and glaciers
0.592%
0.014%
Soil
moisture
0.0005%
Rivers
0.0001%
Atmospheric
water vapor
0.0001%
Fig. 15-2 p. 307
Water Cycle: Renewing Water
Surface Water
Surface runoff: precipitation that does not
infiltrate the ground or return to the atmosphere.
Reliable runoff: the amount of water that
can be counted on each year as a stable source.
Surface Runoff
Watershed: the
region of land
from which
surface water
drains into a
river, lake,
wetland or
other body of
water
Watershed
Delaware
River
Watershed
Groundwater
• One of the most
important source of
water.
• Precipitation filters
down through pores
and cracks in soil and
rocks.
• Groundwater found
within 1km of the
surface contains 100
times more water than
all the rivers, streams
and lakes
Ground Water
Flowing
artesian well
Precipitation
Well requiring a pump
Evaporation and transpiration
Evaporation
Confined
Recharge Area
Runoff
Aquifer
Infiltration
Stream
Water table
Lake
Infiltration
Unconfined aquifer
Less permeable material
such as clay
Confined aquifer
Confirming permeable rock layer
Fig. 15-3 p. 308
Use of Water Resources
 Humans use about 54% of reliable runoff
 Agriculture:
worldwide about 70%
of water is used to
irrigate crops.
85% of that is not
returned to the water
ways.
United States
Power
cooling
38%
Agriculture
38%
Industry 11%
Public 10%
Fig. 15-4 p. 309
Use of Water Resources
• Industry: 20% of water
withdrawn each year is
used by industry.
• Domestic: 10% is used
by cities and residencies.
Uses of Water
Water in US East vs. West
• Eastern US most water
is used for energy
production,
manufacturing.
• Western US most water
is used for irrigation.
Water in US East vs. West
Chapter 15 Sections 1-2 Review
• Where is the world’s usable water located?
• Describe several properties of water that make it
unique.
• How much water is available for human usage?
• What is runoff? What is a watershed? What is
groundwater?
• Describe the water cycle.
• How is most of the world’s water used?
• What are some water differences between the
eastern and western US?
Key Concepts Chapter 15
Sections 3, 4 and 5
• What causes fresh water shortages?
• How many people do not have access to clean
water?
• How can we increase clean water supplies?
• What are advantages and disadvantages of large
dams and reservoirs?
• Case Studies: 1) Water Conflicts in the Middle East,
2) Colorado River Basin, 3) China’s Three Gorges
Dam, 4) Aral Sea, 5) California Water Transfer, 6)
Canada’s James Bay Watershed.
Access to Freshwater
• About 1 in 6 people (1 billion people) do not
have access to regular, clean water supplies.
Too Little Water
What
causes fresh
water
shortages?
Acute shortage
Adequate supply
Shortage
Metropolitan regions with
population greater than 1 million
Fig. 15-6 p. 310
Areas of US
where there
are conflicts
over water.
“Water
Wars”
competing
for a scarce
resource.
Too Little Water: 4 Reasons
Dry climate: people
living or growing
crops in areas where
little precipitation
naturally falls
• San Diego averages
just 8 inches of rain a
year compared to
over 35 inches in
Camden.
Las Vegas averages less than 5
inches of rain yearly.
Too Little Water
Drought:
prolonged
periods of
below average
precipitation.
Too Little Water
Desiccation: drying
of exposed soil
because of activities
such as
deforestation and
overgrazing.
Too Little Water
Water stress: low per
capita availability of
water due to increasing
population demands.
• Some regions get plenty of
water, but not near where
people live
• Some regions get plenty of
water, but not at the right
time of year
• Some regions have no
capacity to store water.
Natural Capital Degradation. Stress on the
world’s river basins.
Increasing Water Supplies
1) Build dams and
reservoirs
2) Transfer water to places
it is needed
3) Withdraw groundwater
4) Desalinization
5) Reduce water waste
6) Import food from
regions where irrigation
is not needed.
Using Dams and Reservoirs
Large dams can
produce cheap
electricity, reduce
downstream
flooding and
provide a yearround source of
water, but they
completely alter
the river
ecosystem.
Using Dams and Reservoirs to
Supply More Water: The Trade-offs
Flooded land destroys
forests or cropland and
displaces people
Large losses
of water through
evaporation
Downstream cropland and
estuaries are deprived of
nutrient-rich silt
Downstream flooding
is reduced
Reservoir is useful for
recreation and fishing
Can produce cheap electricity (hydropower)
Migration and spawning of some fish are disrupted
Provides water
for year-round
irrigation of
cropland
Fig. 15-9 p. 313
Transferring Water from One Place
to Another
Watershed transfer
CALIFORNIA
NEVADA
Sacramento
River
California
Water Project
North Bay
Aqueduct
Shasta Lake
Sacramento
San Francisco
South Bay
Aqueduct
Central
Arizona Project
Fresno
Los Angeles
Aqueduct
California Aqueduct
James Bay
UTAH
Los Angeles
Colorado
River
ARIZONA
Central Arizona
Project
Phoenix
San Diego Colorado River
Aqueduct
Tucson
MEXICO
Fig. 15-13 p. 317
Sections 3,4 and 5 Review
• What causes fresh water shortages?
• How can we increase clean water supplies?
• What are advantages and disadvantages of
large dams and reservoirs?
• Case Studies: 1) Water Conflicts in the Middle
East, 2) Colorado River Basin, 3) China’s
Three Gorges Dam, 4) Aral Sea, 5) California
Water Transfer, 6) Canada’s James Bay
Watershed.
Key Concepts Chapter 15
Sections 6 and 7
• What are advantages and disadvantages of using
groundwater?
• Deep water or shallow water aquifers, what about
desalinization?
• “Weird” Water Solutions?
• What are the benefits of reducing water waste?
• How can we reduce wasting irrigation water? What
about in homes, industry and businesses?
Tapping Groundwater: Benefits
Most
aquifers
are
renewable
sources
unless the
water is
removed
faster than
it is
replenished
Tapping Groundwater: Benefits
Year-round use:
aquifers provide
reliable year-round
use.
• ¼ of world’s drinking
water
• In US groundwater is
being withdrawn 4
times its replacement
rate.
Tapping Groundwater: Benefits
Little Water Loss:
there is no loss of water
due to evaporation.
Often Cheaper:
groundwater is often
cheap to extract.
Tapping Groundwater: Costs
Using ground water
has tradeoffs.
Water tables around
the world are
falling.
Problems Using Groundwater
Problems with Using Groundwater
Water table lowering
Depletion
Subsidence
Saltwater intrusion
Chemical contamination
Reduced stream flows
Potential Sources of Groundwater
Contamination
Problems with Using Groundwater
As groundwater is
pumped out of
the ground, the
ground may
subside.
This picture
shows ground
subsidence in
CA.
Problems Using Groundwater
Salt Water Intrusion:
As water is pumped
out of ground,
saltwater can move
inland to “pollute”
the well.
Problems Using Groundwater
Increasing Water Supplies
Distillation desalination: removing salt
from seawater by evaporation of water leaving
salt behind.
Increasing Water Supplies
Reverse osmosis desalination: pumping
saltwater under high pressure through a
membrane to take out salt.
Increasing Water Supplies
Desalination is very
expensive: only several
oil-rich and water
poor countries use
large-scale
desalinization.
TAKES TREMENDOUS
AMOUNT OF
ENERGY
• Future Potential???
Increasing Water Supplies
Cloud Seeding:
releasing tiny
particles into air to
produce rain clouds.
Towing Icebergs:
moving ice around
world.
Using Oil Tankers
Filled with water.
Using Water More Efficiently
 Reduce losses due to leakage: we waste
about 2/3rd of the water we use, but simple
steps could reduce that to 15%.
Using Water More Efficiently
Reform water laws:
• Higher water prices
• Typically US farmers
only pay 1/5th of true
water costs.
• Encouraging
conservation
• Reward people for
using less water
Using Water More Efficiently
Improve irrigation
efficiency: 60% of
water applied to land
does not reach crops.
• Evaporation
• Seepage
• Runoff
Using Water More Efficiently
Improve irrigation
efficiency:
• Center pivot
sprinklers
• Time controlled
irrigation
• Soil moisture detectors
• Drip Irrigation
Using Water More Efficiently
Water efficient
landscaping
(xeriscaping): using
vegetating that does not
require much water.
• About 1/5th of all US
water houses do not
have water meters and
pay a flat rate.
Using Water More Efficiently
Water efficient
appliances:
• Low Flow Toilets
• Washers that use less
water
Reusing water:
Using “brownwater” for
non-drinking water
usages.
Chapter 15 Sections 6, 7 Review
• What are advantages and disadvantages of
using groundwater?
• Deep water or shallow water aquifers, what
about desalinization?
• “Weird” Water Solutions?
• What are the benefits of reducing water waste?
• How can we reduce wasting irrigation water?
What about in homes, industry and businesses?
Chapter 15 Section 8 and 9
•
•
•
•
What causes flooding?
How do humans exacerbate flooding?
How can flood risks be minimized?
What are solutions for sustainable water
use?
Too Much Water: Floods
 Natural phenomena
 Aggravated by human activities
Natural floodplain, altered floodplain and flooded.
Reservoir
Dam
Levee
Flood
wall
Floodplain
Fig. 15-24 p. 327
Too Much Water: Floods
Natural Events: heavy
rainfall, melting
snow are major
causes of flooding.
Floodplain: the natural
area around a river
where flooding
normally occurs.
Too Much Water: Floods
Floodplains are
usually fertile,
have ample water
for irrigation and
therefore often
developed.
Floods bring
nutrients onto
surrounding land.
Too Much Water: Floods
Flooding Worsens With
Human Impacts:
• Removing wetlands
• Building levees
• Making more land
impermeable
(development)
Downstream Impacts
Too Much Water: Floods
Reducing Risks:
• Channelization
• Floodwalls
• Build Dams
• Preserve wetlands
• Identify and restrict
building in
floodplains
• Restore natural land
Solutions: Achieving a More
Sustainable Water Future
Efficient irrigation
Water-saving technologies
Improving water management
See Fig. 15-26 p. 329