Chapter 14 Water: A Limited Resource

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Chapter 14Water A Limited Resource
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Overview of Chapter 14

• Importance of Water
• Hydrologic Cycle
• Water Use and Resource Problems
• Too Much Water
• Too Little Water
• Water Problems in US and Canada
• Global Water Problems
• Sharing Water Resources
• Water Management
• Providing Sustainable Water Supply
• Water Conservation

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Importance of Water

• Moderates the climate, and allows organisms to
  survive
• 97 of the Earths water is salty and not
  available for use by terrestrial organisms
• humans use 54 of the Earths accessible,
  renewable fresh water
• Cooking
• Washing
• Use large amounts for
• Agriculture
• Manufacturing
• Mining
• Energy production
• Waste disposal
• Use of freshwater is increasing

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Properties of Water

• Composed of 2 Hydrogen and 1 oxygen
• Exists as solid, liquid or gas
• Polar
• One end has () charge, one end has (-) charge
• Forms Hydrogen bond between other water molecules
• H-bonds define waters physical properties
• High melting/freezing point and high boiling
  point
• High heat capacity
• Universal solvent
• Expands when heated, contracts when cold

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Properties of Water

• Water is never completely pure in nature
• Content of seawater (left)
• Many substances water dissolves cause water
  pollution

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Hydrologic Cycle
Describes how water continuously circulates
through the environment
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Distribution of Water

• Only 2.5 of water on earth is freshwater
• 2 is in the form of ice!
• Only 0.5 of water on earth is available
  freshwater

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Freshwater Terminology

• Surface water
• Precipitation that remains on the surface and
  does not seep into soil
• Runoff
• Movement of surface water to lakes, rivers, etc.
• Watershed (drainage basin)
• Land area that delivers water into a stream or
  river system
• Groundwater
• Freshwater under the earths surface stored in
  aquifers
• Aquifer
• Underground caverns and porous layers of sand,
  gravel and rock in which groundwater is stored
• Unconfined aquifer (UA) has porous rock layers
  above it
• Upper limit of UA is water table
• Confined aquifer/Artesian Well
• Groundwater storage area between impermeable
  layers of rock

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Freshwater Aquifer
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Water Use and Resource Problems

• The greatest user of water worldwide is
  agriculture (71 for irrigation, 20 for
  industry, 9 for domestic and municipal use)
• Problems Fall into Three Categories
• Too much water
• Too little water
• Poor quality/contamination (discussed in Chapter
  22)

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Too Much Water

• Flooding
• Both natural and human-induced
• Modern floods are highly destructive because
  humans
• Remove water-absorbing plant cover from soil
• Construct buildings on floodplains
• Floodplain
• Area bordering a river channel that has the
  potential to flood

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Pre-Urban vs. Urban Floodplains
Transpiration the loss of water vapor from the
aerial surfaces of plants
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Floodplain

• Government restrictions on building
• Levees can fail

• Rather than rebuild levees adjacent to rivers,
  experts suggest allowing some flooding of
  floodplains during floods
• (next slide)

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Left Traditional levees adjacent to river
Right Suggested levee style, set back from river
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Case-In-Point Floods of 1993

• Mississippi River flooded
• Covered 23 million acres
• 50 killed
• 12 billion in damages
• 70,000 homes lost
• 8.7 million acres of farmland
• Draining wetlands, building on flood plains, and
  levees made problem worse

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Too Little Water

• Typically found in arid land
• Problems
• Drought
• Overdrawing water
• for irrigation
• purposes
• Aquifer depletion
• Subsidence
• Sinkholes

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Too Little Water

• Problems (continued)
• Saltwater Intrusion
• Seawater moves into a freshwater aquifer

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Water Problems In US and Canada

• US has a plentiful supply of freshwater
• Many areas have a severe shortages
• Geographical variations
• Seasonal variations

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Water Problems in US and Canada

• Water shortages in West and Southwest
• Water is diverted and transported via aqueducts

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Water Problems in US and Canada- Surface Water

• Mono Lake (Eastern CA)
• Rivers and streams that once fed this lake are
  diverted to Los Angeles (275mi away)
• Becoming highly saline
• Court ordered water diversion reduction
• Colorado River Basin
• provides water for 27 million people irrigates
  3.5 million acres of crops
• 1922 Colorado River Compact stipulates an annual
  allotment of 7.5 million acre-feet of water to
  the lower Colorado average annual flow was
  overestimated
• Mexico receives a share of the Colorado
  stipulated by a 1944 treaty
• The Colorado River water is often completely
  consumed before it can reach the Pacific Ocean
  in places, it is saltier than the ocean

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Colorado River bed in Mexico
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Water Problems in US and Canada-Groundwater

• Aquifer Depletion
• 50 of the U.S. population uses groundwater for
  drinking
• 40 of water used for irrigation in the U.S.
  comes from groundwater
• Saltwater intrusion often results from removal of
  too much groundwater

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Global Water Problems

• Amount of freshwater on planet CAN meet human
  needs
• BUT, it is unevenly distributed and some places
  lack stable runoff
• Problems
• Climate Change
• Drinking Water
• Population Growth
• Sharing Water Resources Among Countries

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Global Water Problems

• Water and Climate Change
• Climate change affects the type and distribution
  of precipitation
• Potential issues
• Reduced snowfall will impact water resources
  downstream
• Sea level rise will cause saltwater intrusion
  into drinking water supplies

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Global Water Problems

• Drinking Water Problems
• Many developing countries have insufficient water
  to meet drinking and household needs
• 1.1 billion people lack access to safe drinking
  water
• 2.6 billion people are without access to a
  satisfactory means of domestic wastewater and
  fecal waste disposal
• Population Growth
• Increase in population means an increase in
  freshwater requirements
• Limits drinking water available
• Limits water available for agriculture (food)

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Global Water Problems

• Sharing Water Resources Among Countries
• Rhine River Basin (right)
• Countries upstream discharged pollutants into
  river
• Countries downstream had to pay to clean the
  water before they could drink it
• International Commission for Protection of the
  Rhine (ICPR) help clean up Rhine in 1986
• Spurred by massive chemical spill
• Successful return of Atlantic Salmon

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Aral Seastraddles Kazahkhstan and Uzbekistan

• Water diversion for irrigation has caused sea to
  become too saline
• Lots of health problems
• All 24 species of fish are gone
• Currently the area is recovering thanks to
  funding from the World Bank

1967
1997
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Global Water Problems

• Potentially Volatile International Water
  Situations
• Jordan River
• Supplies water to Israel, Jordan, West Bank, and
  Gaza Strip
• Nile River
• 10 nations use water but the majority is used by
  Egypt

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Water Management

• Main Goal Provide sustainable supply of
  high-quality water
• Requires humans to use resource carefully
• Dams and Reservoirs
• Water Diversion Projects
• Desalinization

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Dams and Reservoirs

• Benefits
• Ensure year-round supply of water with regulated
  flow
• Generate electricity
• Provide recreational activities
• Disadvantages
• Alter the ecosystem
• Reduce sediment load

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Dams and Reservoirs

• Glen Canyon Dam
• Built in 1963
• Regulated flow has changed ecosystem in Colorado
  River and Grand Canyon
• To rectify situation
• Canyon has been flooded several times
• Small floods compared to natural floods
• Still helps rebuild habitat

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Dams and Reservoirs

• Salmon Population in Columbia River is very low
  due to dams that impede migration
• Hatchery efforts not working
• Fish ladders help, but are not effective enough
• Most controversial plan involves removal of
  several dams on the Snake River

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Water Diversion Projects

• Requires diverting water to areas that are
  deficient by pumping through a system of
  aqueducts
• Much of CAs receives its water supply from
  diverted water from Northern CA
• Controversial and expensive

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Desalinization

• Removal of salt from ocean or brackish water
• Two methods
• Distillation- salt water is evaporated, and water
  vapor is condensed into freshwater (salt left
  behind)
• Reverse Osmosis- involves forcing salt water
  through a membrane permeable to water, but not
  salt
• Very expensive

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Water Conservation

• Reducing Agricultural Water Waste
• Agriculture is very inefficient with water
• Microirrigation- irrigation that conserves water
  by piping it to
• crops through sealed
• systems
• Also called drip or
• trickle irrigation

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Water Conservation

• Reducing Industrial Water Waste
• Stricter laws provide incentive to conserve water
• Recycling water within the plant
• Water scarcity (in addition to stricter pollution
  control requirements) will encourage further
  industrial recycling
• Potential to conserve water is huge!

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Water Conservation

• Reducing Municipal Water Waste
• Gray Water
• Used water (e.g. from sinks)
• Can be used to flush toilets, wash car or water
  lawn
• Water saving household fixtures
• Government incentives
• Charge more for water during dry periods

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Conserving at Home

• Install water-saving shower heads and faucets
• Install low-flush toilets
• Fix leaky fixtures
• Purchase high efficiency appliances
• Modify personal habits
• Use the dishwasher instead of washing by hand