Water by chenmeixiu



        Chapter 15
Water Wars
 Water shortage
 Growing population
 Poor irrigation efficiency

 Economic competition- importing more grain
  to reduce need for irrigation water or work out
  water-sharing agreements with other
Unique Properties of Water
 Strong hydrogen bonds
 Liquid over wide temperature range
 High heat capacity – changes temperature
  slowly (moderates climate, used as coolant
  for car engine & power plants)
 Large amount of energy needed to evaporate
  – heat is then released during condensation
  (helps distribute heat & determine climate
  zones; evaporation/sweating = cooling
 Dissolves many substances- dissolves
  nutrients in living tissue, flush waste out of
  tissues, all-purpose cleanser, helps
  remove/dilute water-soluble waste
 Filters out UV radiation that would harm
  aquatic organisms
 Bonds – allow capillary action – water can
  move upward through plants
 Expands when frozen= ice floats; prevents
  lakes & streams from freezing solid
Available Freshwater
 Only 0.014% is available for useh
Water Cycle
 Surface runoff- water flowing off the land into
  bodies of surface water
 Reliable runoff- amount of run-off that we can
  generally count on as a stable source of
 Watershed (drainage basin)- region from
  which surface water drains into a river, lake,
  wetland, or other body of water
 Groundwater- water stored in spaces in soil &
 Zone of aeration- close to surface; pore
  space contains mixture of air & water
 Zone of saturation- lower layers of soil where
  pore space is filled with water
 Water table- top of zone of saturation
 Aquifer- (deep) porous, water-saturated
  layers of sand, gravel, or bedrock through
  which groundwater flows
 Natural recharge- natural replenishment of an
  aquifer by precipitation, which percolates
  downward through soil & rock

 Shortages result from:
 Removing groundwater faster than it is
 Some aquifers receive little, if any recharge
Water Use
 Withdrawal- total amount of water removed
  from lake, river, or aquifer for any purpose

 Consumptive water use- withdrawn water is
  not available for reuse in basin due to losses
  like evaporation, seepage into ground,
  transportation to another area, or
Water Use
 Population- up 3x
 Global water withdrawal- up 7x
 Per capita withdrawal- up 4x

 Reliable surface runoff used- 34%
 Used by 2025- 70% (90% if per capita rises
 Irrigation- 70%
 Industry- 20%
 Residences & cities- 10%
Eastern U.S.
 Major water use- energy production, cooling,
  & manufacturing

 Problems- flooding, occasional urban
  shortages, pollution
Western U.S.
 Major water use- irrigation

 Problems- shortage of runoff, low
  precipitation / high evaporation, recurring
  prolonged drought
Causes of Water Scarcity
 Dry climate
 Drought- prolonged period with 70% less
  precipitation & higher than normal
 Dessication- drying of exposed soil due to
  deforestation or overgrazing
 Water stress- low per capita availability due to
  high population relying on limited runoff
Increase Freshwater Supply
 Build dams & reservoirs to store runoff
 Bring in surface water from another area
 Desalinization
 Reduce water waste
 Import food to reduce water use in crops &
 Withdraw groundwater
Government Ownership
- Poor management & efficiency
+ Strict government oversight
+ Equal access & fair rates
Private Ownership
+ Funds & management expertise
+ Improved efficiency, good job
- No rate control
- Profitable
- Sold as a luxary, not basic need
                                                                      cropland and
                     Flooded land
                                                                      estuaries are
                     destroys forests
                                                                      deprived of
                     or cropland and
                                                                      nutrient-rich silt
                     displaces people
  Large losses
  of water through
                                                             flooding is

                                                                                   Provides water
                                                                                   for year-round
                                                                                   irrigation of

                          Reservoir is   Can produce
                                                             Migration and
Figure 15-9               useful for
                          and fishing
                                         cheap electricity
                                         (hydropower)        spawning of
                                                             some fish are

Page 313
Colorado River Dams
+ Provides electricity from numerous
   hydroelectric plants
+ Provides water for 7 states
+ Multibillion dollar recreational industry
   (whitewater rafting, boating, fishing, camping,
- Arid area
- Legal pacts allocating water supply for US &
- River water rarely makes it to Guld of
- Threatens aquatic spawning
- Destroys estuaries
- Increases saltwater contaminated coastal
                 China’s Three Gorges Dam
            Advantages                Disadvantages
Will generate about 10%               Floods large areas of
of China’s electricity                cropland and forests

Reduces dependence                    Displaces 1.9 million people
on coal
                                      Increases water pollution
Reduces air pollution                 because of reduced water
Reduces CO2 emissions
                                      Reduces deposits of nutrient-
                                      rich sediments below dam
Reduces chances of
downstream flooding
for 15 million people                 Increases saltwater
                                      Introduced into drinking water
                                      near mouth of river because
Reduces river sitting
below dam by eroded
                                      of decreased water flow
                                      Disrupts spawning and
Increases irrigation water
                                      migration of some fish
                                      below dam
for cropland below
                                      High cost                      315
Aral Sea Water Transfer Project
 Shrinking of Aral Sea
 Regional ecological, economic, health
 Salinity 3x higher
 Surface area down 58%
 83% water loss
 Feeder rivers reduced to trickles
 Eliminates wetlands
 Birds & mammal species disappeared
 Extinction of 20 (of 24) native fish species
 Salt dust settles on wildlife, crops, & other
California Water Transfer Project
NORTH                   SOUTH
 Degrade Sacramento     Need more water to
  River                   grow crops
 Threatens fisheries    Lakes shrink = reduced
 Reduces flushing of     populations of ducks,
  San Francisco Bay       gulls, & wading birds
 Water sent South is
James Bay in Canada
- 600 dams & dikes that will reverse or alter flow
   of 19 giant rivers
- Will flood boreal forests & tundra
- Displace of indigenous Cree & Inuits
+ Hydroelectric power
                Withdrawing Groundwater
           Advantages                   Disadvantages

Good source of water for                Aquifier depletion from over-
drinking and irrigation                 pumping

                                        Sinking of land (subsidence)
Available year-round                    when water removed

                                        Polluted aquifiers unusable
Exists almost everywhere                for decades or centuries

                                        Saltwater intrusion into
Renewable if not over-                  drinking water supplies near
pumped or contaminated                  coastal areas

                                        Reduced water flows into
No evaporation losses                   streams, lakes, estuaries,
                                        and wetlands

Cheaper to extract than                 Increased cost, energy use,
most surface waters                     and contamination from
                                        deeper wells                Figure 15-15
                                                                      Page 319
Excessive Withdrawal
 Unsustainable water mining
 Limits future food production
 Increases gap between rich & poor areas
 Must drill deeper wells, buy larger pumps, &
  use more electricity
 Causes sinkholes
Saltwater Intrusion
 Movement of salt water into freshwater
  aquifers in coastal & inland areas as
  groundwater is withdrawn faster than it is
  recharged by precipitation

 Groundwater becomes unusable
Ogallala Aquifer
+ Transformed vast areas of arid prairie into
   productive agricultural land
- Slows recharge rate
- Aquifer is thinner for southern region
- Government subsidies increased crop
   production & increases depletion of aquifer
                     Groundwater Depletion
           Prevention                     Control

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

Ban new wells in
aquifiers near surface
                                         Tax water pumped
Buy and retire ground-                   from Wells near
water withdrawal rights in
critical areas
                                         surface water
Do not grow water-
intensive crops in dry
areas                                    Set and enforce

Reduce birth rates
                                         minimum stream flow
Deep Aquifer Concerns:
 Little known about geological & ecological
  impacts of using these aquifers
 No international water treaties govern the
  rights to & ownership of water that underlies
  several countries
- High cost
- Large energy requirements
- Large amounts of briny waste water
- Dumping of waste increases salinity of ocean
   water (food resources & aquatic life
+ Make ocean water or brackish water usable
Seeding Clouds
 Does not work well in very dry areas
 No scientific evidence of success
 Introduces large amounts of chemicals into
  soil & water systems (harms people, wildlife,
  & agricultural productivity)
 Ownership of cloud water
Iceberg Towing
 Unsure methods
 Cost

 Probably neither (iceberg towing or cloud
  seeding) would provide significant amounts of
Wasted Water
 65-70% of world water is wasted
 Could be reduced to 15%
 Causes:
 Underpricing- government subsidies for
  irrigation water, electricity, & diesel fuel for
  farmers to pump water at below-market price
 Lack of government subsidies for improving
  efficiency of water use
Irrigation Systems
 Center pivot- uses pump to spray water on
      80% efficient
      Uses 25% less water
 Drip irrigation- microirrigation- above or below
  ground pipes or tubes deliver water to
  individual plant roots
      90-95% efficient
 Gravity flow- water flow into ditches from
  aqueduct or nearby river
      60-80% efficient
  Figure 15-20
  Page 324

                                                                          Center Pivot
                                                                       (efficiency 80% with low-
                                          Drip Irrigation                       pressure
                                          (efficiency 90-95%)         sprinkler and 90–95% with
        Gravity Flow                                                         LEPA sprinkler)
(efficiency 60% and 80% with surge   Above- or below-ground pipes
              valves)                  or tubes deliver water to     Water usually pumped from
                                        individual plant roots.     underground and sprayed from
  Water usually comes from an                                        mobile boom with sprinklers.
aqueduct system or a nearby river.

    Reducing Irrigation Water Waste

•Lining canals bring water to irrigation ditches

•Leveling fields with lasers

•Irrigating at night to reduce evaporation

•Using soil and satellite sensorsand computer
systems to monitor soil moisture and add water
only when necessary


•Organic Farming                                   Figure
•Growing water-efficient crops using drought-
resistant and salt tolerant crops varieties
•Irrigating with treated urban waste water         Page
•Importing water-intensive crops and meat
          Reducing Water Waste
•Redesign manufacturing processes

•Landscape yards with plants that require little

•Use drip irrigation

•Fix water leaks

•Use water meters and charge for all municipal
water use

•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
Reducing Water Used to Remove
 Use pollution prevention & waste reduction to
  decrease waste production
 Ban toxic wastes in municipal sewer system
 Waterless composting toilet
 Nutrient-rich sludge returned to soil as
 New sewage treatment methods that recycle
  nutrients in organic waste material
+ Fertile soils
+ Ample water for irrigation
+ Rivers for transportation & recreation
+ Flat land suitable for crops, buildings,
  highways, & railroads
- Removal of water-absorbing vegetation
Increasing Flood Damage
 Removal of water-absorbing vegetation
 Draining wetlands
 Living on floodplains
 Pavement & buildings
 Straighten & deep streams
 Build levees or floodwalls
 Build dams
 Preserve existing wetlands & restore
  degraded wetlands
 Identify & manage flood-prone areas
 Think carefully about where we live

Figure                    Sustainable Water Use
         • Not depleting aquifers

15-26    • Preserving ecological health of
           aquatic systems

Page     • Preserving water quality

         • Integrated watershed management
329      • Agreements among regions and
           countries sharing surface water

         • Outside party mediation of water
           disputes between nations

         • Marketing of water rights

         • Raising water prices

         • Wasting less water

         • Decreasing government subsides for
           supplying water

         • Increasing government subsides for
           reducing water waste

         • Slowing population growth
                         What Can You Do?
                        Water Use and Waste

Figure   • Use water-saving toilets, showerheads, and faucet aerators

         • Shower instead of taking baths, and take short showers.
15-27    • Repair water leaks.

Page     • Turn off sink faucets while brushing teeth, shaving, or

330      • Wash only full loads of clothes or use the lowest possible
           water-level setting for smaller loads.

         • 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

         • Water lawns and garden in the early morning or evening.

         • Use drip irrigation and mulch for gardens and flowerbeds.

         • Use recycled (gray) water for watering lawns and
           houseplants and for washing cars.

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