7. Have students pick out finished products in your classroom or home and, beginning with the raw materials,
trace the use of water in giving you the final product.
8. If a dam has been constructed or is being built in your area, visit the site with your class. Ask students to
find pictures of the area and its water control problems before the dam was built, evaluate whether the dam
should have been built, and substantiate their claims. Were there alternatives to dam construction? What is
the expected lifetime of the dam?
9. Have your class identify the present or potential sources of contaminants in your community’s drinking
water supply. If surface water from a river or lake is used, how and to what degree is it being polluted
before it is withdrawn for your use? If groundwater is used, is the aquifer subject to contamination by
leaking sanitary landfills, improperly functioning septic tanks, uncontained hazardous wastes, or other
sources of pollution? (Ask a public health and/or environmental official to discuss these problems with
10. Ask your students to explore the principal sources of industrial water pollution in your community. What
specific types of chemicals are removed in the treatment of these industrial wastes? How is this
accomplished?
11. With your class, take a field trip to the nearest lake, river, or stream, preferably with a biologist. Note its
smell, appearance, taste (if safe), flow, and ecological characteristics. How have these changed over the
past 20 years? What plants and animals do you find living in or near the water? What are their functions? If
12. With your class, visit the nearest reservoir, pond, or lake and try to find evidence of natural eutrophication
and human-induced eutrophication. How deep is the body of water? How do depth and water quality vary
throughout the year? How old is the body of water? What factors appear to limit growth of organisms in the
body of water? What might the normal life span of the body of water be? Its actual life span? If possible,
Attitudes and Values Assessment
1. Do you consume too much water? Does your community consume too much water? How will climate
change affect your local freshwater supplies?
2. Do you feel your community is doing enough to provide water? Do you feel other strategies should be
tried?
3. Is your community growing too fast? Are you confident that your community has an adequate water supply
for the needs of the community for the next decade? Do you feel other strategies should be tried?
7. Do you favor increasing the price of irrigation water to reflect its true cost and encourage conservation
among farmers? How do you think that might affect food prices? Would you be willing to pay more?
8. Do you favor local ordinances that conserve water (such as the low-use toilet requirement for new
housing)?
9. Would you support sharp increases in monthly water bills for all homes, buildings, and industries to
discourage water waste?
10. Do you believe that bottled water is higher quality water than your local tap water?
Laboratory Skills
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #12: Colorimetric Determination of Free
Chlorine in Drinking Water.
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #13: Life in a Watershed.
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #14: Know Your Neighborhood.
News Videos
Kalahari Desert Could Double in Size, The Brooks/Cole Environmental Science Video Library 2009, ©2011,
DVD ISBN-13: 978-0-538-73355-7
Half the World Denied Basic Sanitation, The Brooks/Cole Environmental Science Video Library 2009,
©2011, DVD ISBN-13: 978-0-538-73355-7
Oil Crisis in the Gulf of Mexico, The Brooks/Cole Environmental Science Video Library 2010 with Workbook,
©2012, DVD ISBN-13: 978-0-538-73495-0
Additional Video Resources
Chapter 11: Water Resources and Water Pollution
After the Storm (Documentary, free DVD or VHS)
Looks at watersheds and their importance in various parts of the U.S.
http://www.epa.gov/weatherchannel/video.html
We All Live Downstream (Documentary, 1991)
Web Resources
UN-Water
Information about regional UN-Water initiatives and statistics about water resources.
http://www.unwater.org/
World Health Organization
Water Sanitation Health information.
http://www.who.int/water_sanitation_health/en/
Instructor’s Manual for Environmental Science, 15th edition
Waterkeeper Alliance
Nearly 200 Waterkeeper Organizations on six continents defend their communities against anyone who
threatens their right to clean water.
http://www.waterkeeper.org/
Digital Integration
Correlation to Global Environment Watch
Aquifers
California
Coral Reefs
Dams
Desalination
Deserts and Desertification
Forests and Deforestation
Global Environment Watch:
Water
Gulf of Mexico Oil Spill
2010
Human Health
Natural Disasters
Oceans and Seas
Sanitation
Sustainable Agriculture
Sustainable Cities
Water
Correlation to Explore More
Aquaculture
Aquatic Ecosystems
China
Overfishing
Water Pollution
Water Resources
Suggested Answers to End of Chapter Questions
Answers will vary but these represent phrases from this chapter. The following are examples of the material that
Review
Core Case Study
1. Summarize the importance of the Colorado River basin in the United States and how human activities are
stressing this system. Define drought and explain how it has affected the Colorado River system.
• The Colorado River is the major river of the arid southwestern United States. During the past 50 years, this
once free-flowing river has been tamed by a gigantic plumbing system consisting of 14 major dams and
Chapter 11: Water Resources and Water Pollution
livestock. The river also supplies water to major cities such as Las Vegas, San Diego, and Los Angeles and
Section 11-1
2. What are the two key concepts for this section? Define freshwater. Explain why access to water is a health issue,
an economic issue, a national and global security issue, and an environmental issue. What percentage of the
earth’s freshwater is available to us? Explain how water is recycled by the hydrologic cycle and how human
activities can interfere with this cycle. Define groundwater, zone of saturation, water table, aquifer, surface water,
surface runoff, watershed (drainage basin), and reliable surface runoff.
• CONCEPT 11-1A We are using available freshwater unsustainably by wasting it, polluting it, and not
charging enough for this irreplaceable natural resource.
• CONCEPT 11-1B One of every six people does not have adequate access to clean water, and this
situation will almost certainly get worse.
• Freshwater is water that is relatively pure and contains few dissolved salts.
• Only a tiny fraction of the planet’s abundant water supply—about 0.024%—is readily available to us
as liquid freshwater in accessible groundwater deposits and in lakes, rivers, and streams.
• The world’s freshwater supply is continually collected, purified, recycled, and distributed in the earth’s
hydrologic cycle—the movement of water in aquatic systems, in the air, and on land, which is driven
by solar energy and gravity.
• This water recycling and purification system works well, unless we overload it with pollutants or
withdraw freshwater from underground and surface water supplies faster than it is replenished. We can
also alter long-term precipitation rates and distribution patterns of freshwater through our influence on
projected climate change.
• Some precipitation infiltrates the ground and percolates downward through spaces in soil, gravel, and
rock until an impenetrable layer of rock stops it. The freshwater in these spaces is called groundwater.
• The spaces in soil and rock close to the earth’s surface hold little moisture. Below a certain depth, in
the zone of saturation, these spaces are completely filled with water.
• The top of this groundwater zone is the water table. It falls in dry weather, or when we remove
groundwater faster than nature can replenish it, and it rises in wet weather.
Instructor’s Manual for Environmental Science, 15th edition
• According to hydrologists, two-thirds of the annual surface runoff of freshwater into rivers and streams
is lost in seasonal floods and is not available for human use. The remaining one-third is reliable surface
runoff, which we can generally count on as a source of freshwater from year to year.
• According to the U.S. Geological Survey, about 79% of the water used in the United States is used for
irrigating crops (40%) and removing heat from electric power plants (39%). In the East, most water is
used for power plant cooling and manufacturing.
3. What percentage of the world’s reliable runoff are we using and what percentage are we likely to be using by
2025? How is most of the world’s water used? Define water footprint and virtual water and give two
examples of each. Describe the availability and use of freshwater resources in the United States and the
water shortages that could occur during this century. What are four major problems resulting from the way
people are using water from the Colorado River basin? What percentage of the earth’s land suffers from
severe drought today and how might this change by 2059? How many people in the world lack regular
access to clean water today?
Two-thirds of the annual surface runoff in rivers and streams is lost by seasonal floods and is not available
for human use. The remaining one-third is reliable surface runoff, which we can generally count on as a
source of freshwater from year to year.
• Some water experts project that because of a combination of population growth, rising rates of water use
per person, longer dry periods in some areas, and failure to reduce unnecessary water losses, we are
likely to be withdrawing up to 90% of the reliable freshwater runoff by 2025.
• Agriculture accounts for 92% of humanity’s water use.
• Problems from water overuse on the Colorado River: economic and ecological disruptions with political and
legal battles over who will get how much of the region’s greatly diminished freshwater supply. Agricultural
production would drop sharply and the region’s major desert cities such as Las Vegas, Nevada (which
depends on the Colorado for more than 90% of its freshwater needs), and Phoenix, Arizona, would be
challenged to survive.
Chapter 11: Water Resources and Water Pollution
• In 2012, the United Nations (UN) and the WHO reported that about 780 million people—nearly 2.5 times the
U.S. population—did not have regular access to enough clean water for drinking, cooking, and washing,
mostly due to poverty.
SECTION 11-2
4. What are the three key concepts for this section? What are the advantages and disadvantages of
withdrawing groundwater? Summarize the problem of groundwater depletion in the world and in the
United States, especially in the Ogallala aquifer. List two problems that result from the overpumping of
aquifers. List some ways to prevent or slow groundwater depletion.
• CONCEPT 11-2A Groundwater used to supply cities and grow food is being pumped from aquifers in
some areas faster than it is renewed by precipitation.
• CONCEPT 11-2B Using dams, reservoirs, and water transfer projects to provide water to arid regions has
increased freshwater supplies in some areas but has disrupted ecosystems and displaced people.
• CONCEPT 11-2C We can convert salty ocean water to freshwater, but the cost is high and the resulting
large volume of salty brine must be disposed of without harming aquatic or terrestrial ecosystems.
• Figure 11-7 Tradeoff of withdrawing groundwater. Advantages include:
o Useful for drinking and irrigation.
o Exists almost everywhere.
o Renewable if not overpumped or contaminated.
o Cheaper to extract than most surface waters.
• Disadvantages include:
o Aquifer depletion from overpumping.
• Withdrawing large amounts of groundwater sometimes allows the sand and rock in aquifers to
collapse. This causes the land above the aquifer to subside or sink, a phenomenon known as land
subsidence and sometimes referred to as a sinkhole. Once an aquifer becomes compressed by
subsidence, recharge is impossible. In addition, land subsidence can damage roadways, water and
sewer lines, and building foundations.
• Groundwater overdrafts near coastal areas, where many of the world’s largest cities and industrial
areas are found, can pull saltwater into freshwater aquifers. The resulting contaminated groundwater is
undrinkable and unusable for irrigation. This problem is especially serious in coastal areas of the U.S.
Instructor’s Manual for Environmental Science, 15th edition
• Scientists are evaluating deep aquifers as future sources of freshwater. Preliminary results suggest that
some of these aquifers hold enough freshwater to support billions of people for centuries. In addition,
the quality of freshwater in these aquifers may be much higher than the quality of the freshwater in
most rivers and lakes. There are four major concerns about tapping these ancient deposits of
5. What is a dam? What is a reservoir? What are the advantages and disadvantages of using large dams and
reservoirs? What has happened to water flows in the Colorado River (Core Case Study) since 1960? List three
possible solutions to the supply problems in the Colorado River basin. List the pros and cons of the California
Water Project. Describe the environmental and health disaster caused by the Aral Sea water transfer project.
Define desalination and distinguish between distillation and reverse osmosis as methods for desalinating water.
What are three limitations of desalination?
• Large dams are structures built across rivers to block some of the flow of water.
• Reservoirs store water collected behind the dams.
• See Figure 11-12. Trade-offs: advantages and disadvantages of large dams and reservoirs.
• Since 1905, the amount of water flowing to the mouth of the heavily dammed Colorado River has
dropped dramatically as a result of multiple dams, water withdrawals for agriculture and urban areas,
and prolonged drought. In most years since 1960, the river has dwindled to a small, sluggish stream by
the time it reaches the Gulf of California. This threatens the survival of aquatic species that spawn in
• See CASE STUDY: California Transfers Massive Amounts of Freshwater from Water-Rich Areas to
Water-Poor Areas.
• See CASE STUDY: The Aral Sea Disaster: A Striking Example of Unintended Consequences.
• Desalination involves removing dissolved salts from ocean water or from brackish (slightly salty)
water in aquifers or lakes for domestic use. It is another way to increase supplies of freshwater. The
two most widely used methods for desalinating water are distillation and reverse osmosis. Distillation
involves heating saltwater until it evaporates (leaving behind salts in solid form) and condenses as
freshwater. Reverse osmosis (or microfiltration) uses high pressure to force saltwater through a
Chapter 11: Water Resources and Water Pollution
Section 11.3
6. What is the key concept for this section? What percentage of available freshwater is lost through inefficient
use and other causes in the world and in the United States? What are two major reasons for those losses?
Describe three major irrigation methods and list ways to reduce water losses in irrigation. List four ways to
reduce water waste in industries and homes and three ways to use less water to remove wastes. How does
flooding affect water supplies and what are three ways in which we can reduce our contribution to
flooding? List four ways in which each of us can reduce our water footprint.
• Concept 11-3 We can use freshwater more sustainably by cutting water waste, raising water prices,
slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release
freshwater.
• About 66% of the freshwater used in the world and about 50% of the freshwater used in the United
States is unnecessarily wasted.
• One reason that water is wasted is that the cost of freshwater to users is low. Such underpricing is
mostly the result of government subsidies that provide irrigation water, or the electricity and diesel fuel
• A second reason for water waste is a lack of government subsidies for improving the efficiency of
freshwater use. Withdrawing environmentally harmful subsidies that encourage freshwater waste and
replacing them with environmentally beneficial subsidies for more efficient freshwater use would
sharply reduce freshwater waste and help to reduce shortages of freshwater.
• Four irrigation methods include:
o Flood irrigation method delivers far more water than is needed for crop growth and typically loses
40% of the water through evaporation, seepage, and runoff. This system obtains water from a
• See Figure 11-16. Methods for reducing water waste in irrigation.
o Line canals bringing water to irrigation ditches.
o Irrigate at night to reduce evaporation.
o Monitor soil moisture to add water only when necessary.
o Grow several crops on each plot of land (polyculture).
• See Figure 11-18. Methods of reducing water waste.
o Redesign manufacturing processes to use less water.
o Recycle water in industry.
o Landscape yards with plants that require little water.
Instructor’s Manual for Environmental Science, 15th edition
o Purify and reuse water for houses, apartments, and office buildings.
• We save water used to remove wastes by using systems that mimic the way nature deals with wastes
by recycling them.
o Return the nutrient-rich sludge produced by conventional waste treatment plants to the soil as a
fertilizer.
o Ban the discharge of toxic industrial chemicals into sewage treatment plants so that the nutrient-
rich sludge from these plants would be too toxic to apply to cropland soils.
o Rely more on waterless composting toilets.
Section 11-4
7. What is the key concept for this section? What is water pollution? Distinguish between point sources and
nonpoint sources of water pollution and give an example of each. List nine major types of water pollutants and
give an example of each. Summarize the relationship between atmospheric warming and water pollution.
See pages 256–257.
• CONCEPT 11-5 Reducing water pollution requires that we prevent it, work with nature to treat sewage cut
resource use and waste, reduce poverty, and slow population growth.,
• Water pollution is any change in water quality that harms humans or other living organisms or makes
8. Explain how streams can cleanse themselves and how these cleansing processes can be overwhelmed. What is
wastewater? Describe the state of stream pollution in developed and developing countries. Give two reasons why
lakes cannot cleanse themselves as readily as streams can. Distinguish between eutrophication and cultural
eutrophication. List ways to prevent or reduce cultural eutrophication. Explain why groundwater cannot cleanse
itself very well. What are the major sources of groundwater contamination in the United States? List ways to
prevent or clean up groundwater contamination. List some ways to purify drinking water. Describe the
environmental problems caused by the widespread use of bottled water.
• Flowing rivers and streams can recover rapidly from moderate levels of degradable, oxygen-
demanding wastes through a combination of dilution and bacterial biodegradation of such wastes. But
this natural recovery process does not work when streams become overloaded with such pollutants or
when drought, damming, or water diversion reduces their flows. Also, while this process can remove
biodegradable wastes, it does not eliminate slowly degradable and nondegradable pollutants.
• Half of the world’s 500 major rivers are heavily polluted, and most of these polluted waterways run
through less-developed countries.
• Lakes and reservoirs are generally less effective at diluting pollutants than streams for two reasons.
First, deep lakes and reservoirs often contain stratified layers that undergo little vertical mixing.
Second, they have little or no flow. The flushing and changing of water in lakes and large artificial
reservoirs can take from 1 to 100 years, compared with several days to several weeks for streams.
• Eutrophication is the name given to the natural nutrient enrichment of a shallow lake, estuary, or slow-
moving stream. It is caused mostly by runoff of plant nutrients, such as nitrates and phosphates, from
surrounding land. An oligotrophic lake is low in nutrients and its water is clear. Over time some lakes
become more eutrophic as nutrients are added from natural and human sources in the surrounding
watersheds.
• Near urban or agricultural areas, human activities can greatly accelerate the input of plant nutrients to a
lake—a process called cultural eutrophication. Mostly nitrate- and phosphate-containing effluents in
runoff from various sources cause this change. These sources include farmland, animal feedlots, urban
Instructor’s Manual for Environmental Science, 15th edition
dispersed effectively. In addition, groundwater usually has much lower concentrations of dissolved
oxygen (which helps decompose many contaminants) and smaller populations of decomposing
bacteria. The usually cold temperatures of groundwater also slow down chemical reactions that
decompose wastes.
• See Figure 11-26 Natural capital degradation: Principal sources of groundwater contamination in the
United States. An EPA survey of 26,000 industrial waste ponds and lagoons found that one-third of
them had no liners to prevent toxic liquid wastes from seeping into aquifers. One-third of these sites
• Clean-up includes:
o Pump to surface, clean, and return to aquifer (very expensive).
o Inject microorganisms to clean up contamination (less expensive but still costly).
o Pump nanoparticles of inorganic compounds to remove pollutants (still being developed).
• Since 1970, most of the world’s more-developed countries have enacted laws and regulations that have
significantly reduced point-source water pollution.
9. Why should we care about the oceans? How are coastal waters and deeper ocean waters polluted? What causes
algal blooms and what are their negative effects? Describe oxygen depletion in the northern Gulf of Mexico.
What are the effects of oil pollution of the oceans and what can be done to reduce such pollution? How can we
prevent or reduce pollution of coastal waters?
• Coastal areas—especially wetlands, estuaries, coral reefs, and mangrove swamps—bear the brunt of
our enormous inputs of pollutants and wastes into the ocean. See Figure11-29 Natural capital
degradation: Residential areas, factories, and farms all contribute to the pollution of coastal waters.
• Runoff of sewage and agricultural wastes into coastal waters introduces large quantities of nitrate and
10. List ways to reduce water pollution from (a) nonpoint sources and (b) point sources. Describe the U.S. experience
with reducing point-source water pollution and list way to improve such efforts. What is a septic tank and how
does it work? Explain how primary sewage treatment and secondary sewage treatment are used to help purify
water. How could we improve conventional sewage treatment? What is a composting toilet system? Describe
John Todd’s use of living machines to treat sewage. Explain how wetlands can be used to treat sewage. List six
ways to prevent and reduce water pollution. List five things you can do to reduce water pollution. What are this
chapter’s three big ideas? Explain how the three scientific principles of sustainability can guide us in using water
resources more sustainably and in reducing and preventing water pollution.
• Nonpoint-source water pollution may be reduced by farmers keeping cropland covered with
vegetation, decreasing the amount of fertilizer that runs off into surface waters by using slow-release
fertilizer, using no fertilizer on steeply sloped land, and planting buffer zones of vegetation between
cultivated fields and nearby surface waters.
• Most developed countries have enacted laws and regulations that have significantly reduced point-
source water pollution as a result of bottom-up political pressure on elected officials by individuals and
groups.
• See CASE STUDY: U.S. Experience with Reducing Point-Source Water Pollution.
• In the United States, the Federal Water Pollution Control Act of 1972 (renamed the Clean Water Act
when it was amended in 1977) and the 1987 Water Quality Act form the basis of U.S. efforts to control
pollution of the country’s surface waters. The Clean Water Act sets standards for allowed levels of 100
key water pollutants and requires polluters to get permits that limit how much of these various
Instructor’s Manual for Environmental Science, 15th edition
• See Figure 11-33 for ways to prevent and reduce water pollution.
o Prevent groundwater contamination.
o Reduce nonpoint runoff.
o Reuse treated wastewater for irrigation.
o Find substitutes for toxic pollutants.
o Work with nature to treat sewage.
Critical Thinking
1. What do you think are the three most important priorities for dealing with the water resource problems of
the Colorado River basin, as discussed in the Core Case Study that opens this chapter? Explain your
choices.
Answers will vary but may be related to the water supply being challenged by too little, poor quality, and
2. What role does population growth play in water supply problems? Relate this to water supply problems of the
Colorado River basin (Core Case Study).
3. Explain why you are for or against: (a) raising the price of water while providing lower lifeline rates for the
poor and lower middle class, (b) withdrawing government subsidies that provide farmers with water at low
cost, and (c) providing government subsidies to farmers for improving irrigation efficiency.
4. Calculate how many liters (and gallons) of water are wasted in 1 month by a toilet that leaks 2 drops of
water per second. (One liter of water equals about 3,500 drops and 1 liter equals 0.265 gallon.) How many
bathtubs (each containing about 150 liters or 40 gallons) could be filled with this lost water?
Given: Loss of water from leaking toilet.
2 drops of water per second
1 liter=3,500 drops
1 liter=0.265 gallons
1 bathtub = 40 gallons
Calculation: loss of water per month
366 gallons/month ÷ 40 gallons/tub = 9.15 bathtubs/month
5. List the three most important ways in which you could use water more efficiently. Which, if any, of these
measures do you already take?
Student answers will vary.
Ways to use water more efficiently include:
• Use water-saving toilets, showerheads, and faucet aerators.
• Shower instead of taking baths, and take short showers.
• Repair water leaks.
• Turn off sink faucets while brushing teeth, shaving, or washing.
6. How might you be contributing directly or indirectly to the annual dead zone that forms in the Gulf of
Mexico? What are three things you could do to reduce your contribution?
Student answers will vary but may focus most directly on the use of that area as being highly agricultural.
7. How might you be contributing directly or indirectly to groundwater pollution? What are three things you could
do to reduce your contribution?
8. When you flush your toilet, where does the wastewater go? Trace the actual flow of this water in your community
from your toilet through sewers to a wastewater treatment plant (or to a septic system) and from there to the
environment. Try to visit a local sewage treatment plant to see what it does with wastewater. Compare the
processes it uses with those shown in Figure 11.32. What happens to the sludge produced by this plant? What
improvements, if any, would you suggest for this plant?
Student answers will vary:
Global Environment Watch Exercise
Search for Ogallala Aquifer and research the decline of this aquifer. Plot the decline on a graph and list the
three areas over the aquifer where the decline is the worst. Look for projections on how much more the
aquifer could decline in the future and take notes on this. Find information on the causes of this decline and
determine which the three largest causes are. Learn what is being done to address each of these causes and
write a report explaining the causes, projections, and possible ways to slow the decline of the Ogallala
Aquifer.
Ecological Footprint Analysis
1. Based on total freshwater use:
a. Calculate the per capita consumption of water per day in Florida in 2005 and the projected per capita
consumption per day for 2025.
b. Calculate the per capita consumption of water per year in Florida in 2005 and the projected per capita
Chapter 11: Water Resources and Water Pollution
2025 per capita daily consumption:
32,075,471,000 liters per day (8,500,000,000 gallons per day) / 25,900,000 people = 1238 liters/person/day
(328 gallons/person/day)
2. In 2005, how did Florida’s average water footprint (consumption per person per year), based only on water
used within the state, compare with the average U.S. water footprint of approximately 249,000 liters
(66,000 gallons) per person per year and the global average water footprint of 123,770 liters (32,800
gallons) per person per year?