Environment in the News
nayo0f033
chapter_10.pptFreshwater Resources and Water Pollution
Chapter 10
Drought in Australia
- The Murray-Darling Basin supports the city of Adelaide and provides 65% of water used by Australia’s agriculture
- Currently threatened after 8 years of drought
- About 40% of Australia’s crops are raised in this semi-arid region
- Farmers compete with city residents
- Environment is changing
- Lakes become salty, native species die, wetlands become toxic, ethnologically important plants and animals have been lost
- Environmental and economic damage
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The Importance of Water
Learning Objectives:
Explain how processes of the hydrologic cycle allow water to circulate through the abiotic environment
Describe the structure of a water molecule and explain how hydrogen bonds form between adjacent water molecules
List the unique properties of water
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The Importance of Water
- Life on Earth would be impossible without water
- All living organisms contain water
- Humans are approximately 60% water
- Uses:
- Drinking, cooking, washing, travel on it, agriculture, manufacturing, mining, energy production, waster disposal
- Less than 3% of Earth’s water is consumable
- 97% is salty
- Uneven distribution - serious regional supply issues
- By 2025, more than 1/3 of humans will live in areas with inadequate supply of drinking/irrigation water
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The Importance of Water
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The Importance of Water
- The Hydrologic Cycle and Our Supply of Freshwater
- Water circulates in the environment
- Provides balance of water in ocean, land, atmosphere
- Renews supply of freshwater on land
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The Importance of Water
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The Importance of Water
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The Importance of Water
- Surface Water:
- Precipitation that remains on the surface of the land and does not seep down through the soil
- Runoff:
- Drainage basin/watershed:
- Groundwater:
- The supply of freshwater that is stored in underground aquifers (underground reservoirs)
- Considered a non-renewable resource, takes 100s–1000s of years to form
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The Importance of Water
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The Importance of Water
- Properties of Water
- Molecules of H2O
- Polar molecules
- The O end of the molecule has negative charge
- The H end of the molecule has positive charge
- Hydrogen bonds
- Form between 2 molecules of H2O due to opposite charges of the two ends of each molecule
- Responsible for many physical properties of water
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The Importance of Water
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Global Climate Change
What is surface water?
How do hydrogen bonds form between adjacent water molecules?
What are the unique properties of water?
Water Resource Problems
Learning Objectives
Relate some of the problems caused by aquifer depletion, overdrawing of surface waters, and salinization of irrigated soil
Relate the background behind the water problems of the Ogallala Aquifer and the Colorado River Basin
Briefly describe the role of international cooperation in managing shared water resources
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Water Resource Problems
Three categories:
- Too much water
- Too little water
- Poor-quality water
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Water Resource Problems
- Flooding
- Occurs when a river’s discharge cannot be contained within its normal channel
- Humans remove water-absorbing plant cover and construct buildings on flood plains
- Area bordering a river channel that has the potential to flood
- Construction replaces flood-protecting plant cover
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Water Resource Problems
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Water Resource Problems
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Water Resource Problems
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Water Resource Problems
- Too little water
- Arid lands: desert
- Plant growth is limited by lack of precipitation
- Semiarid lands:
- Receive more precipitation than deserts, but have long periods of drought
- Farmers use irrigation to increase agricultural productivity of arid and semi-arid lands
- Amount of irrigated land has tripled
- 71% of world’s total water is used for irrigation
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Water Resource Problems
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Water Resource Problems
- Aquifer Depletion
- Results form excessive removal of groundwater, faster than it can be recharged by precipitation or melting snow
- Lowers the water table
- The upper surface of the saturated zone of groundwater
- Subsidence (sinking of the land)
- In areas with porous sediments
- Saltwater intrusion
- Movement of seawater into a freshwater aquifer near the coast
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Water Resource Problems
- The Ogallala Aquifer
- Largest groundwater deposit in the world
- Farmers are drawing water 40 times faster than it can be replaced by nature
- Water table has been lowered 30m (100ft)
- Water conservation esp. through water-saving irrigation will postpone aquifer depletion
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Water Resource Problems
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Water Resource Problems
- Overdrawing of Surface Waters
- Wetlands dry up
- Estuaries become saltier
- Serve as breeding grounds for many species
- Play vital role in water cycle
- Water shortages have great economic and ecological ramifications
- Water supply and Water quality problems
- West and Southwest US, Florida
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Water Resource Problems
- Colorado River Basin
- Serious water problems in US
- Provides water for 30 million people
- Provides irrigation for 3.5 million acres
- International and State laws and agreements
- Insufficient water supply for upper Colorado populations and Mexico - violates agreements
- Colorado river water is saltier than the ocean in some places
- California has agreed to reduce the amount of water withdrawn
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Water Resource Problems
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Water Resource Problems
- Salinization of Irrigated Soil
- Gradual accumulation of slat in soil, often as a result of improper irrigation methods
- Normally, precipitation runoff would carry away salts
- Salt accumulation becomes poisonous for plants
- May render soil unfit for crop production
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Water Resource Problems
- Global Water Issues
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Water Resource Problems
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Water Resource Problems
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Water Resource Problems
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Water Resource Problems
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Water Resource Problems
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Water Resource Problems
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Water Resource Problems
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Global Climate Change
What problems are associated with overdrawing surface water? With aquifer depletion?
What issues surround water problems of the Ogallala Aquifer? The Colorado River basin?
How does international cooperation affect shared water resources?
Water Management
Learning Objectives:
Define sustainable water use
Contrast the benefits and drawbacks of dams and reservoirs
Give examples of water conservation in agriculture, industry, and individual homes and buildings
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Water Management
- Sustainable water use:
- The wise use of water resources, without harming the essential functioning of the hydrologic cycle or the ecosystems on which present and future humans depend
- Conservation:
- Includes reusing and recycling water, improving water use efficiency.
- Important part of sustainable use
- Economic Policies:
- If water is cheap, it tends to be wasted
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Water Management
- Dams and Reservoirs:
- Dams generate electricity and ensure year-round supply of water
- Costs vs. Benefits
- Columbia River - 4th largest in North America
- More than 100 dams generate electricity and provide water
- Negative impact on fish populations
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Water Management
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Water Management
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Water Management
- Water Conservation
- Reducing agricultural water waste
- Reducing water waste in industry
- Reducing municipal water waste
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Water Management
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Water Management
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Global Climate Change
What is sustainable water use?
What are the benefits of dams on the Columbia River? The drawbacks?
How can individuals conserve and manage water resources?
Water Pollution
Learning Objectives:
Define water pollution
Discuss how sewage is related to eutrophication, biochemical oxygen demand (BOD), and dissolved oxygen
Distinguish between the two types of pollution sources and give examples of each
Describe sources of groundwater pollution
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Water Pollution
- A physical or chemical change in water that adversely affects the health of humans and other organisms
- Sewage
- Disease-causing agents
- Sediment pollution
- Inorganic plant and algal nutrients
- Organic compounds
- Inorganic chemicals
- Radioactive substances
- Thermal pollution
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Water Pollution
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Water Pollution
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Water Pollution
- Sewage:
- Wastewater from drains or sewers; includes human wastes, soaps, and detergents
- Disease-causing agents, threat to public health
- Enrichment
- Biochemical Oxygen demand (BOD)
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Water Pollution
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Water Pollution
- Eutrophication:
- Lakes, estuaries, slow-flowing streams
- Oligotrophic:
- Unenriched, clear water, supports small populations of aquatic organisms
- Eutrophic:
- Cloudy water because of the large number of algae and cyanobacteria.
- Water is enriched with inorganic plant and algal nutrients such as Nitrogen and phosphorous
- This can be a natural, long-term process, or
- Artificial eutrophication:
- Overnourishment of an aquatic ecosystem by nutrients due to human activities such as agriculture and discharge from sewage treatment plants
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What a Scientist Sees
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What a Scientist Sees
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Water Pollution
- Sources of Water Pollution
- Point Sources
- Pollutants can be traced to specific sources, such as pipes, sewers, ditches from specific sites
- Non-point Sources
- Pollutants enter a body of water over large areas rather than a specific, single point of entry, i.e. precipitation washes pollutants out of soil and into the water: polluted runoff
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Water Pollution
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Water Pollution
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Water Pollution
- Groundwater Pollution
- Half of the US obtains drinking water from groundwater sources
- Quality is a concern
- Pesticidides, fertilizers, organic compounds seep into groundwater from landfills, storage tanks, backyards, golf courses, etc.
- Cleanup is not always technically feasible
- Very costly
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Water Pollution
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Global Climate Change
What is water pollution?
How does point source pollution differ from nonpoint source pollution? What are some examples of each?
What is biochemical oxygen demand? How is BOD related to sewage?
What are some common sources of groundwater pollutants?
Improving Water Quality
Learning Objectives:
Describe how most drinking water is purified in the United States
Distinguish among primary, secondary, and tertiary treatments for wastewater
Compare the goals of the Safe Drinking Water Act and the Clean Water Act
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Improving Water Quality
- Removing contaminants from water supply before and after use
- Purification of drinking water
- Municipal water supplies are treated before water is used
- Turbid water treated with chemical coagulant to clump and settle out particles
- Filtration through sand to remove microorganisms
- Disinfection (Chlorine, Ozone, UV) to kill any remaining disease-causing organisms
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Improving Water Quality
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Improving Water Quality
- Municipal Sewage Treatment
- Primary Treatment
- Mechanical processes (screening, gravitational settling) to remove suspended and floating particles
- Primary Sludge
- Secondary Treatment
- Biological treatments of wastewater to decompose suspended organic material
- Reduces water’s BOD
- Secondary sludge = mixture of bacteria-laden solids
- Tertiary Treatment
- Advanced treatment. Not always used.
- Biological, chemical, and physical processes
- Reduces N and P, purifies water for reuse
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Improving Water Quality
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Improving Water Quality
- Disposal of Primary and Secondary Sludge
- Artificial wetlands to treat reclaimed water
- Orlando Wetland Park,
- 16 million gal per day, on 1220 acres
- Wetlands absorb and assimilate contaminants
- Provides wildlife habitat
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Improving Water Quality
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Improving Water Quality
- Controlling Water Pollution
- Legislation is effective on point-sources
- 2 very successful laws, but much work is still needed
- Safe Drinking Water Act - 1974
- Uniform federal standards for drinking water
- Guarantees safe drinking water supply
- EPA must determine maximum contaminant levels allowed
- 1996 amendment requires municipalities to inform which contaminants are present and in what amount
- Clean Water Act - 1977
- Quality of rivers, lakes, aquifers, estuaries, and coastal waters
- Eliminate discharge of pollutants in US waterways
- Attain water quality levels that are safe for fishing and swimming
- EPA required to monitor national emissions limitations
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Improving Water Quality
- Preventing Water Pollution at Home
- Individuals produce vey little, but collective effect is large
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Improving Water Quality
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Improving Water Quality
- Water Pollution in developing countries
- 1.4 billion people in the world do not have access to safe drinking water
- 2.9 billion don’t have access to sanitation systems
- 250 million cases of water related illness/yr
- 5 million or more result in death
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Improving Water Quality
- Municipal water pollution is a greater problem in developing countries
- Sewage from densely populated cities is dumped directly into rivers and coastal harbors
- Ganges River-India’s holy river
- Used for bathing and washing clothes
- Very polluted by untreated sewage and industrial waste, and ashes of 35,000 humans/yr
- China
- Severe water safety issues in densely populated issues
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Improving Water Quality
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Improving Water Quality
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Global Climate Change
How is most drinking water purified in the United States?
What are the stages in municipal sewage treatment? What happens in each stage?
How was the Safe Drinking Water Act affected US water supplies? How was the Clean Water Act affected them?
Case Study
- China’s Three Gorges Dam
- World’s largest dam on world’s longest River
- Initiated to control devastating flooding of Yangtze River
- 26 hydroelectric generators = 50 million tons of coal
- Raised water levels, 1million people relocated
- Fragmented habitats
- Fish species in decline
- Spawning conditions altered, migratory routes blocked
- Rare species endangered
- River dolphin, finless porpoise
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