Chapter 14

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					Chapter 14

  Water
     Chapter Overview Questions
 Why is   water so important, how much
  freshwater is available to us, and how much
  of it are we using?
 What causes freshwater shortages, and what
  can be done about this problem?
 What are the advantages and disadvantages
  of withdrawing groundwater?
 What are the advantages and disadvantages
  of using dams and reservoirs to supply more
  water?
Chapter Overview Questions (cont’d)
 What are  the advantages and disadvantages
  of transferring large amounts of water from
  one place to another?
 Can removing salt from seawater solve our
  water supply problems?
 How can we waste less water?
 How can we use the earth’s water more
  sustainably?
 What causes flooding, and what can we do
  about it?
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, and 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
 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

   Precipitation                   Evaporation and transpiration Evaporation

Confined
Recharge            Runoff
Area



               Flowing
                                Recharge
               artesian                            Stream Well
                                Unconfined
               well                                requiring a
                                Aquifer
           Infiltration Water                      pump
                        table                                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
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 ofthe 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                 Aquifer depletion from
and irrigation                      overpumping

Available year-                     Sinking of land
round                               (subsidence) from
                                    overpumping
Exists almost
                                    Polluted aquifers for
everywhere
                                    decades or centuries
Renewable if not                    Saltwater intrusion into
overpumped or                       drinking water supplies
contaminated                        near coastal areas

No evaporation                      Reduced water flows
losses                              into surface waters

Cheaper to extract                  Increased cost and
than most surface                   contamination from
waters                              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, theworld’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)




                   from the nonrenewable
 Irrigation systems
 aquifer appear as green dots. Brown dots are
 wells that have gone dry.
                                      Figure 14-9
                       Solutions

                  Groundwater Depletion

     Prevention                    Control

Waste less water                   Raise price of water
                                   to discourage waste
Subsidize water
conservation

Ban new wells in
aquifers near                      Tax water pumped
surface waters                     from wells near
                                   surface waters
Buy and retire
groundwater
withdrawal rights
in critical areas
                                   Set and enforce
Do not grow water-                 minimum stream
intensive crops in                 flow levels
dry areas
                                                          Fig. 14-12, p. 316
 USING DAMS AND RESERVOIRS
   TO SUPPLY MORE WATER

 Large dams   and reservoirs can produce
 cheap electricity, reduce downstream
 flooding, and provide year-round water for
 irrigating cropland, but they also displace
 people and 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).
Case Study: The Colorado Basin – an
       Overtapped Resource
                     Lake Powell,   is
                      the second
                      largest reservoir
                      in the U.S.
                     It hosts one of
                      the hydroelectric
                      plants located on
                      the Colorado
                      River.
                                Figure 14-15
The Colorado River Basin

                 The area
                 drained by this
                 basin is equal to
                 more than one-
                 twelfth of the
                 land area of the
                 lower 48 states.



                             Figure 14-14
                Case Study:
         China’s Three Gorges Dam
 There isa debate over whether the
 advantages of the world’s largest dam and
 reservoir will outweigh its disadvantages.
     The dam will be 2 kilometers long.
     The electric output will be that of 18 large coal-
      burning or nuclear power plants.
     It will facilitate ship travel reducing transportation
      costs.
     Dam will displace 1.2 million people.
     Dam is built over seismatic fault and already has
      small cracks.
                 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
                  can make unproductive
 Transferring water
 areas more productive but can cause
 environmental harm.
     Promotes investment, jobs and strong economy.
     It encourages unsustainable use of water in
      areas water is not naturally supplied.
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 waterfrom the Aral Sea and its two
 feeder rivers mostly for irrigation has created
 a major ecological, economic, and health
 disaster.
     About 85% of the wetlands have been
      eliminated and roughly 50% of the local bird and
      mammal species have disappeared.
     Since 1961, the sea’s salinity has tripled and the
      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 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 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 towing icebergs
 or huge bags filled with freshwater to dry
 coastal areas have all been proposed but are
 unlikely to provide significant amounts of
 freshwater.
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%.
     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
 Sixty percent of the world’s irrigation water is
  currently wasted, but 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 pumped
                             Above- or below-          from underground and
                             ground pipes or tubes     sprayed from mobile
Water usually comes from     deliver water to          boom with sprinklers.
an aqueduct system or a      individual plant roots.
nearby river.
                                                                  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 water-
  short 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
 We can reduce water     use and waste by
 raising the price of water while providing low
 lifeline rates for the poor.
     When Boulder, Colorado introduced water
      meters, water use per person dropped by 40%.
     A 10% increase in water prices cuts domestic
      water use by 3-7%.
 Solutions: Using Less Water to Remove
    Industrial and Household Wastes
 We can mimic the  way nature deals with
 wastes instead of using large amounts of
 high-quality water to wash away and dilute
 industrial and animal wastes.
     Use nutrients in wastewater before treatment as
      soil fertilizer.
     Use waterless and odorless composting toilets
      that convert human fecal matter into a small
      amount of soil material.
          TOO MUCH WATER
 Heavy rainfall, rapid snowmelt, removal of
  vegetation, and destruction of wetlands
  cause flooding.
 Floodplains, which usually include highly
  productive wetlands, help provide natural
  flood and erosion control, maintain high water
  quality, and recharge groundwater.
 To minimize floods, rivers have been
  narrowed with levees and walls, and
  dammed 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
                       Solutions

               Reducing Flood Damage

Prevention                         Control

Preserve forests on                Strengthen and
watersheds                         deepen streams
                                   (channelization)
Preserve and
restore wetlands
in floodplains
                                   Build levees or
Tax all development                floodwalls along
on floodplains                     streams

Use floodplains
primarily for
recharging aquifers,
sustainable
agriculture and                    Build dams
forestry, and
recreation
                                                      Fig. 14-24, p. 331
SOLUTIONS: USING
  WATER MORE
  SUSTAINABLY
 We can use  water more
 sustainably by cutting
 waste, raising water
 prices, preserving
 forests and wetlands in
 water basins, and
 slowing population
 growth.
                 Figure 14-25

				
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