Transcript Chapter 14

Chapter 14
Water
Core Case Study: Water Conflicts in the
Middle East - A Preview
of the Future
 Middle East
 One of the world’s
highest population
growth rates
 water shortages
 Main supply: Nile,
Tigris, Jordan
Figure 14-1
Water Conflicts in the Middle East: A
Preview of the Future
 Disagreement about water rights.
 Currently

No cooperative agreements for use of 158 of the
world’s 263 water basins that are shared by two or
more countries.
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL


Water: life, moderates climate, sculpts land, removes/dilutes wastes and
pollutants, hydrologic cycle.
0.02% = liquid freshwater
WATER’S IMPORTANCE, AVAILABILITY,
AND RENEWAL
Figure 14-2
WATER’S IMPORTANCE, AVAILABILITY,
AND RENEWAL
 The land from which the surface water drains into
a body of water is called its watershed or drainage
basin.
 Groundwater exists too.
Unconfined Aquifer Recharge Area
Evaporation and transpiration Evaporation
Precipitation
Confined
Recharge
Area
Runoff
Flowing
artesian
well
Recharge
Unconfined
Aquifer
Infiltration Water
table
Stream Well
requiring a
pump
Lake
Infiltration
Fig. 14-3, p. 308
Animation: Threats to the Aquifers
Animations/aquifers.html
WATER’S IMPORTANCE, AVAILABILITY,
AND RENEWAL
 70% water withdrawn from rivers, lakes, and
aquifers is not returned to these sources.
 Irrigation (70%), industries (20%) and cities and
residences (10%).
 Currently >50% of the world’s reliable runoff is
used

70-90% by 2025.
Figure 14-4
Case Study: Freshwater Resources in the
United States
 17 western states
face potential
intense water
conflict

urban growth,
irrigation,
recreation and
wildlife.
Figure 14-5
TOO LITTLE FRESHWATER
 41% of the world’s population lives in river basins
that do not have enough freshwater.



Rivers running dry.
Lakes and seas shrinking.
Falling water tables (overpumped aquifers)
Stress on the World’s River Basins
 Comparison of the amount of water available with
the amount used by humans.
Figure 14-6
Case Study: Who Should Own and
Manage Freshwater Resources
 Controversy: government owned and managed or
private corporations.

European-based water companies aim to control 70%
of the U.S. water supply.
TOO LITTLE FRESHWATER
 Cities are outbidding farmers.
 Countries are importing grain.
 More crops used for biofuels.
 Options:

Get more water from aquifers and rivers, desalinate
ocean water, waste less water.
WITHDRAWING GROUNDWATER TO
INCREASE SUPPLIES
 Most aquifers are renewable


Unless water is removed faster than replenished
Or contaminated.
 Groundwater depletion - growing problem


Irrigation.
One-fourth of the farms in India irrigated from
overpumped aquifers.
Trade-Offs
Withdrawing Groundwater
Advantages
Disadvantages
Useful for drinking
and irrigation
Aquifer depletion from
overpumping
Available yearround
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
No evaporation
losses
Reduced water flows
into surface waters
Cheaper to extract
than most surface
waters
Increased cost and
contamination from
deeper wells
Fig. 14-7, p. 313
Groundwater Depletion:
A Growing Problem
 Areas
of greatest aquifer depletion (overdraft)
OGALLALA
Other Effects of Groundwater
Overpumping
 Groundwater
overpumping


Sinkholes
(subsidence)
Contamination with
saltwater. (salt water
intrusion)
Figure 14-11
Other Effects of Groundwater
Overpumping
Figure 14-10
Groundwater Pumping in Saudi Arabia
(1986 – 2004)
Irrigation systems
 Nonrenewable aquifer = green dots
 Dried wells = Brown dots

Figure 14-9
Solutions
Groundwater Depletion
Prevention
Waste less water
Control
Raise price of water
to discourage waste
Subsidize water
conservation
Ban new wells in
aquifers near
surface waters
Tax water pumped
from wells near
surface waters
Buy and retire
groundwater
withdrawal rights
in critical areas
Do not grow waterintensive crops in
dry areas
Set and enforce
minimum stream
flow levels
Fig. 14-12, p. 316
USING DAMS AND RESERVOIRS TO
SUPPLY MORE WATER
 Large dams and reservoirs



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
cheap electricity
reduce downstream flooding
year-round water for irrigating cropland
displace people
disrupt aquatic systems.
Provides water
for year-round
irrigation of
cropland
Provides
water for
drinking
Reservoir is
useful for
recreation
and fishing
Can produce
cheap
electricity
(hydropower)
Downstream
flooding is
reduced
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
Risk of
failure and
devastating
downstream
flooding
Migration and
spawning of
some fish are
disrupted
Fig. 14-13a, p. 317
Powerlines
Reservoir
CLICK ON THIS: http://techalive.mtu.edu/meec/demo/HydroelectricDam.html
Dam
Intake
Powerhouse
Turbine
Fig. 14-13b, p. 317
Case Study: The Colorado Basin – an
Overtapped Resource
 The Colorado River
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


14 major dams and reservoirs, and canals.
Used in desert area of the U.S.
Hydroelectric plants for 30 million people (1/10th of
the U.S. population).
Often doesn’t reach Gulf of California
Case Study: The Colorado Basin – an
Overtapped Resource
 Lake Powell, 2nd
largest reservoir in
the U.S.
 Hydroelectric plant
Figure 14-15
The Colorado River Basin
 Drainage basin
covers more than
one-twelfth of
the land area of
the lower 48
states.
Figure 14-14
Case Study: China’s Three Gorges Dam

DEBATE – world’s largest dam
 Dam 2 km long.
 The electric output = 18 large coal-burning or nuclear power
plants.
 Facilitate ship travel, reduce transportation costs.
 Displace 1.2 million people.
 Built over seismatic fault, already has small cracks.
Dam Removal
 Some for ecological reasons
 Some outlived their usefulness.


In 1998 the U.S. Army Corps of Engineers – no more
large dam projects in US
Federal Energy Regulatory Commission has approved
the removal of nearly 500 dams.
• Can reestablish ecosystems
• Can re-release toxicants into the environment.
TRANSFERRING WATER FROM ONE
PLACE TO ANOTHER
 Transferring water




makes unproductive areas
more productive
can cause environmental
harm.
Promotes investment, jobs
and strong economy.
It encourages unsustainable
use
Case Study: The California Experience
 A massive transfer
of water from
water-rich
northern California
to water-poor
southern California
is controversial.
Figure 14-16
Case Study: The Aral Sea Disaster
 The Aral Sea was once the world’s fourth largest
freshwater lake.
Figure 14-17
Case Study: The Aral Sea Disaster
 Diverting water from the Aral Sea and its two
feeder rivers
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Mostly for irrigation
85% of the wetlands have been eliminated
50% of the local bird and mammal species have
disappeared.
Since 1961,
• sea’s salinity has tripled
• water has dropped by 22 meters most likely causing 20 of
the 24 native fish species to go extinct.
DESALTING SEAWATER, SEEDING
CLOUDS, AND TOWING ICEBERGS AND
GIANT BAGGIES
 Removing salt from seawater = expensive, & large
amounts of salty wastewater

Distillation: heating saltwater until it evaporates,

leaves behind water in solid form.
Reverse osmosis: uses high pressure to force saltwater
through a membrane filter.
DESALTING SEAWATER, SEEDING
CLOUDS, AND TOWING ICEBERGS AND
GIANT BAGGIES
 Seeding clouds with tiny particles of chemicals to
increase rainfall – AgNO3
 towing icebergs or huge bags filled with
freshwater to dry coastal areas

unlikely to provide significant amounts of freshwater.
INCREASING WATER SUPPLIES BY
WASTING LESS WATER

We waste about two-thirds of the water we use
 65-70% lost through evaporation, leaks, and other losses.
 Water is underpriced thru government subsidies.
 Lack of subsidies for improving efficiency contributes to water
waste.
INCREASING WATER SUPPLIES BY
WASTING LESS WATER

60% of the world’s irrigation water is
currently wasted

Improved techniques could
cut this to 5-20%.

Center-pivot, low pressure
sprinklers sprays water directly
onto crop.
• It allows 80% of water to reach
crop.
• Has reduced depletion of
Ogallala aquifer in Texas High
Plains by 30%.
(efficiency 90–95%)
Drip irrigation
Gravity flow
(efficiency 60% and
80% with surge
valves)
Center pivot
Water usually comes from
an aqueduct system or a
nearby river.
Above- or belowground pipes or tubes
deliver water to
individual plant roots.
(efficiency 80%–95%)
Water usually pumped
from underground and
sprayed from mobile
boom with sprinklers.
Fig. 14-18, p. 325
Solutions
Reducing Irrigation Water Waste
• Line canals bringing water to irrigation ditches
• Level fields with lasers
• Irrigate at night to reduce evaporation
• Monitor soil moisture to add water only
when necessary
• Polyculture
• Organic farming
• Don't grow water-thirsty crops in dry areas
• Grow water-efficient crops using drought
resistant and salt-tolerant crop varieties
• Irrigate with treated urban waste water
• Import water-intensive crops and meat
Fig. 14-19, p. 326
Solutions: Getting More Water for
Irrigation in Developing Countries – The
Low-Tech Approach
 Many poor farmers in
developing countries use
low-tech methods to
pump groundwater and
make more efficient use
of rainfall.
Figure 14-20
Solutions
Reducing Water Waste
• Redesign manufacturing processes
• Repair leaking underground pipes
• Landscape yards with plants that
require little water
• Use drip irrigation
• Fix water leaks
• Use water meters
• Raise water prices
• Use waterless composting toilets
• Require water conservation in watershort cities
• Use water-saving toilets, showerheads,
and front loading clothes washers
• Collect and reuse household water to
irrigate lawns and nonedible plants
• Purify and reuse water for houses,
apartments, and office buildings
• Don't waste energy
Fig. 14-21, p. 327
Raising the Price of Water:
A Key to Water Conservation
 Reducing water use and waste

Raising the price of water
• When Boulder, Colorado introduced water meters, water use
per person dropped by 40%.
• A 10% increase in water prices cuts domestic water use by 37%.

Provide low lifeline rates for the poor.
Solutions: Using Less Water to Remove
Industrial and Household Wastes
Mimic the way nature deals with
wastes
 Instead of using large amounts
of high-quality water to wash
and dilute industrial and animal
wastes.
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Use nutrients in wastewater as soil
fertilizer.
Composting toilets convert
human fecal matter into a small
amount of soil material.
TOO MUCH WATER
 FLOODS
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Heavy rainfall
rapid snowmelt
removal of vegetation
destruction of wetlands
 Natural flood mitigation - Floodplains/wetlands =
natural flood and erosion control, maintain high
water quality, and recharge groundwater.
 Artificial flood mitigation
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narrowing rivers with levees and walls
damming to store water.
TOO MUCH WATER
 Comparison of St. Louis, Missouri under normal
conditions (1988) and after severe flooding
(1993).
Figure 14-22
TOO MUCH WATER
 Human activities have contributed to flood deaths
and damages.
Figure 14-23
Animation: Effects of Deforestation
Animations/effects_deforestation.html
Solutions
Reducing Flood Damage
Prevention
Preserve forests on
watersheds
Control
Strengthen and
deepen streams
(channelization)
Preserve and
restore wetlands
in floodplains
Tax all development
on floodplains
Use floodplains
primarily for
recharging aquifers,
sustainable
agriculture and
forestry, and
recreation
Build levees or
floodwalls along
streams
Build dams
Fig. 14-24, p. 331
SOLUTIONS: USING
WATER MORE
SUSTAINABLY
cutting waste
 raising water prices
 preserving forests and
wetlands
 slowing population
growth.

Figure 14-25