Chapter 14 by HC121104175033

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									CHAPTER 14


WATER
         WATER’S IMPORTANCE,
       AVAILABILITY, AND RENEWAL
• Importance of water:
  •   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 CONFLICTS IN THE MIDDLE EAST:


• Most water in this dry region comes from the Nile,
  Jordan or Tigris rivers.
• http://www.youtube.com/watch?v=7RZu4tTp_0U
       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
  (consumptive use).

• 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
         TOO LITTLE FRESHWATER

• About 41% of the world’s population lives in river
  basins that do not have enough freshwater.
  • Reasons
    •   Dry climate
    •   Drought
    •   Too many people use and waste water
    •   Lack of money or gvmt stability to maintain water resources
• 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
               OGALLALA

• http://www.youtube.com/watch?v=3gZWVIv8pB8
   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.
• How would you vote? Private or government ownership
  of water?
       TOO LITTLE FRESHWATER

• Cities are outbidding farmers for water supplies from
  rivers and aquifers.
  • Who should get more water?
• Countries are importing grain as a way to reduce
  their water use.
• BUT More crops are being used to produce biofuels.
  • Why import food but produce biofuel?
• Our water options are:
  • Get more water from aquifers and rivers, desalinate ocean
    water, waste less water.
                  AQUIFERS

• http://www.youtube.com/watch?v=7L06BWmgpCs
                       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
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
                     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.

• Importance of Silt
Provides water   Flooded land
for year-round   destroys forests
irrigation of    or cropland and
cropland         displaces people

                   Large losses of
                   water through
                   evaporation
Provides
water for
drinking          Downstream
                  cropland and
Reservoir is      estuaries are
useful for        deprived of
recreation        nutrient-rich silt
and fishing

                     Risk of
Can produce          failure and
cheap                devastating
electricity          downstream
(hydropower)         flooding
Downstream
flooding is         Migration and
reduced             spawning of
                    some fish are
                    disrupted

                   Fig. 14-13a, p. 317
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).

   • http://www.youtube.com/watch?v=FIPV-H9iCPA
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 is a 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.

 • http://www.youtube.com/watch?v=T2JMVxnMqxU
               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 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
                 • Should water be
                   transferred from
                   northern California to
                   southern California?




                                Figure 14-16
ARAL SEA
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 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.

   • Anthrax buried on island in Aral Sea
 WAYS TO GET MORE FRESHWATER:


• DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS
  AND GIANT BAGGIES



  • Distillation: heating saltwater until it evaporates, leaves behind
    water in solid form.
  • Reverse osmosis: uses high pressure to force saltwater through a
    membrane filter.
  • Both methods are expensive
                        CONT.


• 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.

• http://www.youtube.com/watch?v=Sn5g4Gt_EJw
   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%.
• Low energy precision application sprinklers
  • 90% efficient
• Drip irrigation
  • 95% efficient
                         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
       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.
• What do you think about Tiered water pricing?
  • 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%.
          RETURN TO EQUILIBRIUM

• 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.

• Importance of wetlands, mangrove forests, riparian
  zone
             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
                       What Can You Do?
                       Water Use and Waste
• Use water-saving toilets, showerheads, and faucet aerators.
• Shower instead of taking baths, and take short showers.
• Stop water leaks.
• Turn off sink faucets while brushing teeth, shaving, or washing.
• Flush toilets only when necessary.
• Wash only full loads of clothes or use the lowest water-level for
  smaller loads.
• Use recycled (gray) water for lawn, gardens, house plants,
  car washing.
• Wash a car from a bucket of soapy water, and use the hose for
  rinsing only.
• If you use a commercial car wash, try to find one that recycles its
  water.
• Replace your lawn with native plants that need little if any watering
  and decorative gravel or rocks.
• Water lawns and gardens in the early morning or evening.
• Sweep or blow off driveways instead of hosing off with water.
• Use drip irrigation and mulch for gardens and flowerbeds.             Fig. 14-25, p. 333

								
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