Water, water everywhere and not a drop to drink!

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3.6 Water Resources

• Water, water everywhere and not a drop to drink!

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Connections between water resources and food
resources
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Earths water budget

• Only about 3 of the water on our planet is fresh
  water (97 salt water)
• 69 of fresh water is in polar ice caps and
  glaciers
• 30 is ground water
• The remaining 1 is lakes rivers swamps and in
  the atmosphere

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Human Uses for Fresh water

• Domestic water ( drinking, washing, cleaning)
• Irrigation
• Industry (manufacturing, mining, and
• agriculture)
• Hydroelectric power
• Transportation (ships on lakes/rivers)
• Boundaries (states and nations)

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Water Usage Pie Chart
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Problems related to freshwater use

• Low water levels in rivers, streams and lakes
• Slow water flow
• Underground aquifers become exhausted
• Irrigation causes much of the water to evaporate
  before it can be used.
• Fertilizer and pesticides and industries pollute
  streams
• Industries release warm water into rivers,
  causes dissolved oxygen to decrease (warm water
  contains less Oxygen).

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Solutions

• Reduce domestic use of fresh water (shorter
  showers/wash cars less)
• Irrigation Drought resistant crops- Closed pipes
  instead of open canals
• Reduce farming contamination (pesticides and
  fertilizers).
• Force industry to remove pollutants from
  wastewater

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Case Study The Colorado River An Over tapped
Resource

• 1,429 miles through 7 U.S. states
• Supplies water and electricity 30 million people
  in USA and Mexico
• Heavily dammed for electricity and agriculture
  (14 dams)
• 80 used for irrigation and cattle ranching
• Downstream (in Mexico) can dry up completely some
  years and lead to droughts.
• Salinity problems prevent irrigation in Mexico
• Dried river causes loss of biodiversity

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The Colorado River Basin
Fig. 13-1, p. 317
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Aerial View of Glen Canyon Dam Across the
Colorado River and Lake Powell
Fig. 13-2, p. 317
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A Closer Look at the Over tapped Colorado River
Basin

• Current rate of river withdrawal is not
  sustainable
• Much water used for agriculture that is
  inefficient with water use cotton, alfalfa, rice
• Water use subsidized by government
• Reservoirs
• Leak water into ground below
• Lose much water through evaporation
• Fill up with silt load of river, depriving delta
• Could eventually lose ability to store water and
  create electricity
• States must conserve water, control population,
  and slow urban development

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Water Shortages Will Grow

• Dry climates
• Drought
• Too many people using a normal supply of water
• Wasteful use of water
• 30 earths land area experiences severe drought
• Potential conflicts/wars over water
• Refugees from arid lands
• Increased mortality

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Washington
North Dakota
Montana
Oregon
Idaho
South Dakota
Wyoming
Nebraska
Nevada
Utah
Kansas
Colorado
California
Oklahoma
New Mexico
Arizona
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Fig. 13-5, p. 322
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Natural Capital Degradation Stress on the
Worlds Major River Basins
Fig. 13-6, p. 323
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Is Extracting Groundwater the Answer?

• Groundwater is Being Withdrawn Faster Than It Is
  Replenished
• Most aquifers are renewable
• Aquifers provide drinking water for half the
  world
• Water tables are falling in many parts of the
  world, primarily from crop irrigation

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Water A Replenishable Resource

• India, China, and the United States
• Three largest grain producers
• Over pumping aquifers for irrigation of crops
• Small farmers drilling tube wells
• Effect on water table
• Saudi Arabia
• Aquifer depletion and
• irrigation

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Trade-Offs
Withdrawing Groundwater
Advantages
Disadvantages
Useful for drinking and irrigation
Aquifer depletion from overpumping
Sinking of land from over pumping
Exists almost everywhere
Renewable if not overpumped or contaminated
Pollution of aquifers lasts decades or centuries
Cheaper to extract than most surface waters
Deeper wells are nonrenewable
Fig. 13-7, p. 325
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Is Building More Dams the Answer?

• Main goal of a dam and reservoir system
• Capture and store runoff
• Release runoff as needed to control
• Floods
• Generate electricity
• Supply irrigation water
• Recreation (reservoirs)

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Advantages and Disadvantages of Dams

• Advantages
• Reduce flooding
• Zero emissions electricity production
• Disadvantages
• Displaces people with reservoir
• Impaired ecological services of rivers
• Loss of plant and animal species
• Can cause other streams and lakes to dry up

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Provides irrigation water above and below dam
Flooded land destroys forests or cropland and
displaces people
Large losses of water through evaporation
Provides water for drinking
Deprives downstream cropland and estuaries of
nutrient-rich silt
Reservoir useful for recreation and fishing
Risk of failure and devastating downstream ?ooding
Can produce cheap electricity (hydropower)
Reduces down-stream flooding of cities and farms
Disrupts migration and spawning of some fish
Fig. 13-13a, p. 328
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Is irrigation the answer?

• Case Study The Aral Sea Disaster
• Large-scale water transfers for irrigation stops
  flow of water into the Aral Sea
• Less Water Increase in salinity
• Fish population declines
• Water pollution
• Restoration efforts
• More efficient irrigation
• Dam built to help raise lake level

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Natural Capital Degradation The Aral Sea,
Shrinking Freshwater Lake
Fig. 13-17, p. 332
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Is Desalination the Answer?

• Desalination- Removing Salt from Seawater
• Distillation evaporate water, leaving salts
  behind
• Reverse osmosis, microfiltration use high
  pressure to remove salts
• Problems Very Costly, Kills Organisms, Creates
  Briny Wastewater
• 14,450 plants in 125 countries
• Saudi Arabia highest number

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The Search for Improved Desalination Technology

• Desalination on offshore ships
• Solar or wind energy
• Use ocean waves for power
• Build desalination plants near electric power
  plants

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Deforestation Above Chinas Yangtze River
Contribute to Erosion and Floods
Fig. 13-26, p. 341
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Diverse ecological habitat
Evapotranspiration
Trees reduce soil erosion from heavy rain and wind
Agricultural land
Tree roots stabilize soil
Vegetation releases water slowly and reduces
flooding
Forested Hillside
Fig. 13-25a, p. 340
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Tree plantation
Evapotranspiration decreases
Roads destabilize hillsides
Overgrazing accelerates soil erosion by water and
wind
Winds remove fragile topsoil
Agricultural land is flooded and silted up
Gullies and landslides
Heavy rain erodes topsoil
Silt from erosion fills rivers and reservoirs
Rapid runoff causes flooding
After Deforestation
Fig. 13-25b, p. 340
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Three Big Ideas

• One of the worlds major environmental problems
  is the growing shortage of freshwater in many
  parts of the world.
• We can increase water supplies in water-short
  areas in a number of ways, but the most important
  way is to reduce overall water use and waste by
  using water more sustainably.
• We can use water more sustainably by cutting
  water waste, raising water prices, slowing
  population growth, and protecting aquifers,
  forests, and other ecosystems that store and
  release water.