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					WATER
           World Water Supply
About 70% of Earth’s surface is water.
Of this 70%...
• 97.200% salt water                         Earth's Surface

• 2.800 % fresh Water
    • 02.014% ice caps and glaciers
    • 0.600% is groundwater
    • 0.009% is surface water
    • 0.005% is soil moisture
    • 0.001% is atmospheric moisture
                              Land   Salt Water   Polar Ice Caps   Ground Wate
Global Water Shortages
Global Water Shortage
Why is there a shortage?
Total Water Use
Domestic Use
Industrial Use
Public Supply
Livestock Supply
Water – A Renewable Resource?
• Hydrologic Cycle
  – Transpiration – from plants
  – Evaporation – from rivers, lakes,
    ponds, oceans
  – Precipitation – rain
  – Run off – to rivers, lakes, etc
  – Seepage – to aquifers, groundwater, to
    rivers & oceans, to plants
Surface Water
• Surface water is
  water that is above
  ground in lakes,
  rivers, ponds, and
  streams

• Watershed – the
  entire area of land
  that is drained by a
  river
Mississippi River Basin
Groundwater and Aquifers
• Groundwater – water that seeps down into the
  soil and is stored underground
• Aquifers – large amts of water in underground
  rock formations
• Ex. Edward’s Aquifer (TX)
Ground Water
• Zone of aeration
  – Close to surface
• Zone of saturation
  – Lower layers of
    soil, pores
    completely filled
    with water
• Water table
  – Top of zone of
    saturation
Aquifers
• Confined vs. Unconfined
• Renewable Resource?
                              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
        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
• 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
                       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
                     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
Water Scarcity
• Four Major causes
  – Dry climate

  – Drought

  – Desiccation

  – Water Stress
 Stress on the World’s River Basins




• Comparison of the amount of water available
  with the amount used by humans.
                                            Figure 14-6
Solutions to Water Scarcity - Dams

                  • Dams – Collects
                    water and forms a
                    reservoir (artificial
                    lake)
                  • Reservoir water is
                    used for drinking,
                    manufacturing,
                    irrigation
                  • Used for power and
                    electricity
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).
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.
              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.
Solutions to Water Scarcity –
Moving Water

 • 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
                        • 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 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.
Solutions to Water Scarcity -
Desalinization
 • Desalinization
   – Removing salt from seawater
   – Distillation: heating saltwater until it
     evaporates, leaves behind salt in solid form.
   – Reverse osmosis: uses high pressure to
     force saltwater through a membrane filter.
   – Expensive and produces large amounts of
     salty wastewater that must be disposed of
     safely.
          Distillation




Reverse
Osmosis
Solutions to Water Scarcity – Cloud
Seeding, and more…
• Seeding clouds with
  tiny particles of
  chemicals to increase
  rainfall
• Towing icebergs or
  huge bags filled with
  freshwater to dry
  coastal areas
    Water Conservation
• Though water is
  recycled, the amt of
  usable water at any
  given time is limited
• Solutions: turn water
  faucet off while
  brushing teeth, water
  lawns at night,
  xeriscape (native
  plants)
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
Forested Hillside
              Oxygen
              released by
              vegetation


                     Diverse
                     ecological          Evapotranspiration
                     habitat
                                                 Trees reduce soil
                                                 erosion from heavy
                                                 rain and wind

                                                          Agricultural
                                        Steady            land
                                        river flow

             Leaf litter
             improves soil
             fertility

                 Tree roots stabilize   Vegetation releases
                 soil and aid water     water slowly and
                 flow                   reduces flooding
                                                                 Fig. 14-23a, p. 330
After Deforestation


            Tree plantation


                                           Evapotranspiration decreases
                         Roads
                         destabilize
                                             Ranching accelerates
                         hillsides
                                             soil erosion by water
                                             and wind
                                                         Winds remove fragile
       Gullies and                                       topsoil
       landslides
                                                          Agricultural land is
                                                          flooded and silted up


     Heavy rain leaches
     nutrients from soil and
     erodes topsoil
                                                          Rapid runoff
         Silt from erosion blocks rivers and reservoirs   causes flooding
         and causes flooding downstream
                                                                   Fig. 14-23b, p. 330
                       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.
                SOLUTIONS: USING
• Shower instead of taking baths, and take short showers.
• Stop water leaks. WATER MORE

                      SUSTAINABLY
• Turn off sink faucets while brushing teeth, shaving, or washing.
• Flush toilets only when necessary.
      • We can use water more sustainably by
• Wash only full loads of clothes or use the lowest water-level for
          cutting waste, raising water prices,
  smaller loads.
          preserving forests and wetlands in water
• Use recycled (gray) water for lawn, gardens, house plants,
          basins, and slowing population growth.
  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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