Transcript Chapter 14 - Cloudfront.net

Core Case Study: Water Conflicts in
the Middle East - A Preview
of the Future
 Many
countries in
the Middle East,
which has one of
the world’s highest
population growth
rates, face water
shortages.
Figure 14-1
Water Conflicts in the Middle East: A
Preview of the Future
 Most
water in this dry region comes from the
Nile, Jordan or Tigris rivers.
 Countries are in disagreement as to who has
water rights.
 Currently, there are 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





keeps us alive
moderates climate
sculpts the land
removes and dilutes wastes and pollutants
moves continually through the hydrologic cycle.
 Only
about 0.02% of the earth’s water supply
is available to us as liquid freshwater.
WATER’S IMPORTANCE,
AVAILABILITY, AND RENEWAL
 Comparison
of
population
sizes and
shares of
the world’s
freshwater
among the
continents.
Figure 14-2
WATER’S IMPORTANCE,
AVAILABILITY, AND RENEWAL
 precipitation



infiltrates the ground and is stored in soil and
rock (groundwater)
Evaporates
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
Recharge
Unconfined
Aquifer
Infiltration Water
table
Stream Well
requiring a
pump
Lake
Infiltration
Fig. 14-3, p. 308
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%).
Water in the
United States
 Average
precipitation (top)
in relation to
water-deficit
regions and their
proximity to
metropolitan areas
(bottom).
Figure 14-4
Average annual precipitation (centimeters)
Less than 41
81–122
41–81
More than 122
Fig. 14-4a, p. 309
Acute shortage
Shortage
Adequate supply
Metropolitan regions with population
greater than 1 million
Fig. 14-4b, p. 309
Case Study: Freshwater Resources in
the United States
 17
western states
by 2025 could face
intense conflict over
scarce water
needed for urban
growth, irrigation,
recreation and
wildlife.
Figure 14-5
TOO LITTLE FRESHWATER
 About
41% of the world’s population lives in
river basins that do not have enough
freshwater.
 Many parts of the world are experiencing:



Rivers running dry.
Lakes and seas shrinking.
Falling water tables from 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
 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.
TOO LITTLE FRESHWATER
 Cities
are outbidding farmers for water
supplies from rivers and aquifers.
 Countries are importing grain as a way to
reduce their water use.
 More crops are being used to produce
biofuels.
 Our water options are:



Get more water from aquifers and rivers
desalinate ocean water
waste less water
WITHDRAWING GROUNDWATER
TO INCREASE SUPPLIES
 Most
aquifers are renewable resources
unless water is removed faster than it is
replenished or if they are contaminated.
 Groundwater depletion is a growing problem
mostly from irrigation.

At least one-fourth of the farms in India are being
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
from
groundwater
overdraft in
the
continental
U.S.
 The Ogallala, the world’s largest aquifer, is
most of the red area in the center (Midwest).
Figure 14-8
Other Effects of Groundwater
Overpumping  Groundwater
overpumping
can cause
land to sink,
and
contaminate
freshwater
aquifers near
coastal areas
with
saltwater.
Figure 14-11
Other Effects of Groundwater
Overpumping
 Sinkholes
form when
the roof of an
underground
cavern
collapses
after being
drained of
groundwater.
Figure 14-10
Groundwater Pumping in Saudi
Arabia (1986 – 2004)

Irrigation systems from the nonrenewable aquifer appear as
green dots. Brown dots are wells that have gone dry. 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
produce cheap electricity
reduce downstream flooding
provide year-round water for irrigating cropland
displace people
disrupt aquatic systems
Figure 14-13
Case Study: The Colorado Basin – an
Overtapped Resource
 The
Colorado River has so many dams and
withdrawals that it often does not reach the
ocean.



14 major dams and reservoirs, and canals.
Water is mostly used in desert area of the U.S.
Provides electricity from hydroelectric plants for
30 million people (1/10th of the U.S. population).
The Colorado River Basin
 The
area
drained by this
basin is equal to
more than onetwelfth of the
land area of the
lower 48 states.
Figure 14-14
Dam Removal
 Some
dams are being removed for ecological
reasons and because they have outlived their
usefulness.



In 1998 the U.S. Army Corps of Engineers
announced that it would no longer build large
dams and diversion projects in the U.S.
The Federal Energy Regulatory Commission has
approved the removal of nearly 500 dams.
Removing dams can reestablish ecosystems, but
can also re-release toxicants into the
environment.
TRANSFERRING WATER FROM
ONE PLACE TO ANOTHER
 Transferring

water can:
make unproductive areas more productive
• Promotes:




Investment
Jobs
Strong economy
cause environmental harm
• encourages unsustainable use of water
Case Study: The Aral Sea Disaster
 Aral

Sea
once the world’s 4th largest freshwater lake Figure 14-17
Case Study: The Aral Sea Disaster
 Diversion
of water from the Aral Sea and its
two feeder rivers


Used for irrigation
created a major ecological, economic, and
health disaster
• About 85% of the wetlands have been eliminated
• roughly 50% of the local bird and mammal species
have disappeared
• the sea’s salinity has tripled
• water has dropped by 22 meters

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 by current
methods is expensive and produces large
amounts of salty wastewater that must be
disposed of safely

Distillation:
• heating saltwater until it evaporates, leaves behind
waste in solid form.

Reverse osmosis:
• uses high pressure to force saltwater through a
membrane filter.
INCREASING WATER SUPPLIES BY
WASTING LESS WATER
 We
waste about two-thirds of the water we
use, but we could cut this waste to 15%

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65-70% of the water people use throughout the
world is lost through evaporation, leaks, and
other losses
Water is underpriced through government
subsidies
The lack of government subsidies for improving
the efficiency of water use contributes to water
waste
INCREASING WATER SUPPLIES BY
WASTING LESS WATER
 60%
of the world’s irrigation water is currently
wasted

improved irrigation techniques could cut this
waste 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%.
Drip irrigation
(efficiency 90–95%)
Gravity flow
(efficiency 60% and
80% with surge
valves)
Center pivot
(efficiency 80%–95%)
Water usually comes from
an aqueduct system or a
nearby river.
Above- or belowground pipes or tubes
deliver water to
individual plant roots.
Water usually pumped
from underground and
sprayed from mobile
boom with sprinklers.
Fig. 14-18, p. 325
TOO MUCH WATER
 Human
activities have contributed to flood
deaths and damages.
Figure 14-23