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CHAPTER 11
WATER RESOURCES AND WATER POLLUTION
Outline
11-1 Will we have enough usable water?
A. Freshwater is an irreplaceable resource that we are managing poorly.
2. The earth has a precious layer of water—most of it saltwater—covering about 71% of the
earth’s surface.
3. Water is an irreplaceable chemical with unique properties that keep us and other forms of life
5. Water helps to sculpt the earth’s surface, moderate climate, and remove and dilute wastes and
pollutants.
6. Water is one of our most poorly managed resources.
7. Concerns regarding water include:
a. Access to freshwater is a global health issue. Every day, an average of 3,900 children
younger than age 5 die from waterborne infectious diseases.
b. An economic issue because it is vital for reducing poverty and producing food and
energy.
B. Most of the earth’s freshwater is not available to us.
2. The rest is in the salty oceans, in frozen polar ice caps and glaciers, or in deep underground
and inaccessible locations.
3. The world’s freshwater supply is continually collected, purified, recycled, and distributed in
the earth’s hydrologic cycle—the movement of water in the seas, in the air, and on land,
4. Freshwater is not distributed evenly.
a. Differences in average annual precipitation and economic resources divide the world’s
C. Groundwater and surface water are critical resources.
1. Some precipitation infiltrates the ground and percolates downward through spaces in soil,
gravel, and rock until an impenetrable layer of rock stops this groundwater—one of our most
important sources of freshwater.
Instructor’s Manual for Environmental Science, 15th edition
2. Surface water is the freshwater from precipitation and snowmelt that flows across the earth’s
land surface and into lakes, wetlands, streams, rivers, estuaries, and ultimately to the oceans.
a. Precipitation that does not infiltrate the ground or return to the atmosphere by
body of water is called its watershed, or drainage basin.
D. We use a large and growing portion of the world’s reliable runoff.
2. The remaining one third is reliable surface runoff, which we can generally count on as a
source of freshwater from year to year.
3. During the last century, the human population tripled, global water withdrawals increased
5. Affluent lifestyles require large amounts of water.
6. CASE STUDY: Freshwater Resources in the United States.
a. The United States has more than enough renewable freshwater, but it is unevenly
distributed and much of it is contaminated.
b. About 79% of the water used in the United States is used for irrigating crops (40%) and
removing heat from electric power plants (39%).
c. In the East, most water is used for power plant cooling and manufacturing.
d. In the eastern United States, the most serious water problems are:
i. flooding
f. In the western U.S., the major water problem is a shortage of runoff caused by low
precipitation, high evaporation, and recurring severe drought.
g. Water tables in many water-short areas, especially in the arid and semiarid western half
of the lower 48 states, are dropping quickly as farmers and rapidly growing urban areas
deplete many aquifers faster than they can be recharged
h. At least 36 U.S. states are likely to face water shortages by 2013 because of a
combination of drought, rising temperatures, population growth, urban sprawl, and
7. SCIENCE FOCUS: Water Footprints and Virtual Water
a. Each of us has a water footprint, which is a rough measure of the volume of freshwater
that we use directly and indirectly to keep us alive and to support our lifestyles.
b. The average American each day directly uses about 260 liters (69 gallons) of freshwater.
c. We use much larger amounts of freshwater indirectly to provide us with food and other
consumer products.
d. Freshwater that is not directly consumed but is used to produce food and other products is
called virtual water, and it makes up a large part of our water footprints, especially in
more-developed nations.
E. Freshwater shortages will grow.
1. The main factors that cause water scarcity in any particular area are a dry climate, drought,
2. More than 30 countries—most of them in the Middle East and Africa—now face water
scarcity.
3. By 2050, some 60 countries, many of them in Asia, with three-fourths of the world’s
population, are likely to be suffering from water stress.
5. By 2025, at least 3 billion people are likely to lack access to clean water.
6. We can increase freshwater supplies in various parts of the world by:
a. withdrawing groundwater; building dams and reservoirs to store runoff in rivers for
11-2 How can we increase freshwater supplies?
A. Groundwater is being withdrawn faster than it is replenished in some areas.
2. Most aquifers are renewable resources unless their water becomes contaminated or is
removed faster than it is replenished by rainfall.
3. Water tables are falling in many areas of the world because the rate of pumping water from
4. The world’s three largest grain producers—China, India, and the United States—as well as
Mexico, Saudi Arabia, Iran, Yemen, Israel, and Pakistan are overpumping many of their
aquifers.
B. Case Study: Aquifer Depletion in the United States
2. One of the most serious overdrafts is in the lower half of the Ogallala, the world’s largest
3. In parts of the Ogallala, groundwater is being pumped out 10–40 times faster than the slow
natural recharge rate, which has lowered water tables and increased pumping costs.
4. Serious aquifer depletion is also taking place in California’s semiarid Central Valley, which
supplies half of the country’s fruits and vegetables
C. Overpumping of aquifers has several harmful effects
1. As water tables drop, farmers must drill deeper wells, buy larger pumps, and use more
2. Withdrawing large amounts of groundwater can allows the sand and rock in aquifers to
collapse.
a. This causes the land above the aquifer to subside or sink, a phenomenon known as land
subsidence and sometimes referred to as a sinkhole.
3. Groundwater overdrafts near coastal areas can pull saltwater into freshwater aquifers. The
resulting contaminated groundwater is undrinkable and unusable for irrigation.
4. Deep water aquifers hold enough freshwater to support billions of people for centuries.
5. Concerns about tapping these ancient deposits of freshwater:
a. They are nonrenewable and cannot be replenished on a human timescale.
b. Little is known about the geological and ecological impacts of pumping large amounts of
D. Large dams and reservoirs have advantages and disadvantages
2. Dammed water usually creates a reservoir, a store of water collected behind the dam.
3. A dam and reservoir:
a. capture and store runoff and release it as needed to control floods
4. The world’s 45,000 large dams have increased the annual reliable runoff available for human
use by nearly 33%.
5. Negative effects of dams include:
a. displaced 40–80 million people from their homes
6. Reservoirs eventually fill up with sediments such as mud and silt, typically within 50 years,
which eventually makes them useless for storing water or producing electricity.
7. Around 500 small dams have been removed in the U.S. but removal of large dams is
controversial and expensive.
E. A closer look at the overtapped Colorado River basin.
2. In most years since 1960, the river has dwindled to a small, sluggish stream by the time it
reaches the Gulf of California.
4. As the flow of the rivers slows in reservoirs, it drops much of its load of suspended silt,
5. These reservoirs will probably become too full of silt to control floods and store enough water
6. Agricultural production would drop sharply and many people in the region’s cities likely
would have to migrate to other areas.
7. Withdrawing more groundwater from aquifers is not a solution, because water tables are
already low and withdrawals threaten the survival of aquatic species that spawn in the river,
and destroy estuaries that serve as breeding grounds for numerous other aquatic species.
F. Water transfers can be wasteful and environmentally harmful
2. Such water transfers have benefited many people, but they have also wasted a lot of water and
they have degraded ecosystems from which the water was taken.
3. Such water waste is part of the reason why many products include large amounts of virtual
water.
G. CASE STUDY: California transfers massive amounts of freshwater from water-rich areas to
water-poor areas
5. It uses a maze of giant dams, pumps, and aqueducts to transport water from water-rich
6. This project supplies massive amounts of freshwater to areas that, without such water
transfers, would be mostly desert.
8. Many people living in arid southern California cities, as well as farmers in this area, may have
to move elsewhere because of freshwater shortages.
H. CASE STUDY: The Aral Sea Disaster: A Striking Example of Unintended Consequences.
1. The shrinking of the Aral Sea is the result of a large-scale water transfer project in an area of
the former Soviet Union with the driest climate in central Asia.
3. The sea’s salinity has risen sevenfold and the average level of its water has dropped by 22
meters (72 feet).
5. Winds pick up the sand and salty dust and blow it onto fields as far as 500 kilometers (310
miles) away.
6. The area’s climate is altered. The once-huge sea acted as a thermal buffer that moderated the
heat of summer and the extreme cold of winter. Now there is less rain, summers are hotter and
7. Many of the 45 million people living in the Aral Sea’s watershed have health problems from a
combination of toxic dust, salt, and contaminated water.
8. Since 1999, the United Nations and the World Bank have spent about $600 million to purify
drinking water and upgrade irrigation and drainage systems in the area.
9. The five countries surrounding the lake and its two feeder rivers have worked to improve
10. The Aral Sea basin has been stabilized; nevertheless experts expect the largest portion of the
Aral Sea to continue shrinking.
I. Removing salt from seawater is costly, kills marine organisms, and produces briny wastewater.
1. Desalination involves removing dissolved salts from ocean water or from brackish (slightly
salty) water in aquifers or lakes for domestic use.
2. Today, about 13,000 desalination plants operate in more than 125 countries, especially in the
arid nations of the Middle East, North Africa, the Caribbean, and the Mediterranean.
3. There are three major problems with the widespread use of desalination
a. The high cost, because it takes a lot of increasingly expensive energy to desalinate water.
4. Some scientists have hopes for using solar energy as the primary power source for
desalination.
11-3 How can we use freshwater water more sustainably?
A. Reducing freshwater waste has many benefits.
2. In the United States—the world’s largest user of water—about half of the water drawn
from surface and groundwater supplies is wasted.
4. Reasons so much freshwater is wasted:
a. Government subsidies that keep the cost of freshwater low.
b. Lack of government subsidies for improving the efficiency of freshwater use.
B. We can cut freshwater waste in irrigation.
1. About 60% of the irrigation water applied throughout the world does not reach the
targeted crops.
3. 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.
4. With existing irrigation (see Figure 10-24), this loss could be reduced to 5–10%.
C. We can cut freshwater waste in industry and homes.
1. Producers of chemicals, paper, oil, coal, primary metals, and processed food consume
almost 90% of the water used by industry in the United States.
3. Most industrial processes could be redesigned to use much less freshwater.
4. Flushing toilets with freshwater is the single largest use of domestic water in the United
5. Studies show that 30–60% of the freshwater supplied in nearly all of the world’s major
5. CONNECTIONS: Water Leaks and Water Bills
a. Any water leak unnecessarily wastes freshwater and raises water bills. You can
6. Homeowners and businesses in water-short areas are using drip irrigation on their
properties and replacing lawns with native plants that need little freshwater.
7. About 50–75% of the slightly dirtied water from bathtubs, showers, sinks, dishwashers,
8. The relatively low cost of water in most communities causes excessive water use and
waste.
9. CONNECTIONS: Smart Cards and Water Conservation.
a. In Brazil, an electronic device called a water manager allows customers to obtain
water on a pay-as-you-go basis.
D. We can use less water to remove wastes.
1. Large amounts of freshwater good enough to drink are being flushed away as industrial,
animal, and household wastes.
2. Within 40 years we may need the world’s entire reliable flow of river water just to dilute
and transport the wastes we produce each year.
4. Rely more on waterless composting toilets.
E. We need to use water more sustainably.
1. Each of us can help bring about such a “blue revolution” by using and wasting less water
to reduce our water footprints.
a. Use water-saving toilets, showerheads, and faucet aerators.
b. Shower instead of taking baths, and take short showers.
11-4 How can we deal with water pollution?
A. Water pollution comes from point and nonpoint sources.
1. Water pollution is any change in water quality that harms humans or other living organisms or
makes water unsuitable for human uses such as drinking, irrigation, and recreation.
a. Point sources discharge pollutants at specific locations through drain pipes, ditches, or
sewer lines into bodies of surface water.
Instructor’s Manual for Environmental Science, 15th edition
i. Difficult and expensive to identify and control discharges from many
diffuse sources.
2. CONNECTIONS: Atmospheric Warming and Water Pollution
a. Projected climate change will likely contribute to water pollution in some areas.
b. In a warmer world, some regions will get more precipitation and other areas will get less.
B. Major water pollutants have harmful effects.
2. According to the WHO, an estimated 4,400 people die each day from preventable infectious
diseases that they get from drinking contaminated water.
C. Streams can cleanse themselves, if we do not overload them.
1. Flowing rivers and streams can recover rapidly from moderate levels of degradable, oxygen-
2. This natural recovery process does not work when streams become overloaded with such
pollutants or when drought, damming, or water diversion reduces their flows.
3. INDIVIDUALS MATTER: John Beal Planted Trees to Restore a Stream
a. Hamm Creek is a small stream that flows from the hills southwest of Seattle. It was
once a spawning ground for salmon and its banks were lined by evergreen trees. By
4. Laws enacted in the 1970s to control water pollution have greatly increased the number and
5. Laws also require industries to reduce or eliminate their point-source discharges of harmful
chemicals into surface waters.
6. In most less-developed countries, stream pollution from discharges of untreated sewage,
industrial wastes, and discarded trash is a serious and growing problem.
D. Too little mixing and low water flow make lakes vulnerable to water pollution.
1. Lakes and reservoirs are generally less effective at diluting pollutants than streams.
2. Lakes and reservoirs are more vulnerable than streams to contamination by runoff or
3. Many toxic chemicals and acids also enter lakes and reservoirs from the atmosphere.
4. Eutrophication refers to the natural nutrient enrichment of a shallow lake, estuary, or slow-
5. An oligotrophic lake is low in nutrients and its water is clear.
6. Near urban or agricultural areas, human activities can greatly accelerate the input of plant
nutrients to a lake—a process called cultural eutrophication.
a. During hot weather or drought, this nutrient overload produces dense growths or
“blooms” of organisms, such as algae and cyanobacteria, and thick growths of aquatic
plants.
i. This dense plant life can reduce lake productivity and fish growth by decreasing the
input of solar energy needed for photosynthesis by phytoplankton that support fish.
c. Ways to prevent or reduce cultural eutrophication:
i. Advanced (but expensive) waste treatment to remove nitrates and phosphates before
wastewater enters lakes.
ii. Banning or limiting the use of phosphates in household detergents and other cleaning
agents.
E. Groundwater cannot cleanse itself very well.
2. Common pollutants such as fertilizers, pesticides, gasoline, and organic solvents can seep into
groundwater from numerous sources.
3. When groundwater becomes contaminated, it cannot cleanse itself of degradable wastes as
quickly as flowing surface water does.
4. It can take decades to thousands of years for contaminated groundwater to cleanse itself of
slowly degradable wastes (such as DDT).
5. On a human time scale, nondegradable wastes (such as toxic lead and arsenic) remain in the
water permanently.
F. Groundwater pollution is a serious hidden threat in some areas.
1. Little is known about groundwater pollution because it is expensive to locate, track, and test
aquifers.
3. In 2006, the Chinese government reported that aquifers in about nine of every ten Chinese
cities are polluted or overexploited, and could take hundreds of years to recover.
5. Almost two-thirds of America’s liquid hazardous wastes are injected into the ground in
disposal wells, some of which leak water into aquifers used as sources of drinking water.
6. By 2008, the EPA had completed the cleanup of about 357,000 of the more than 479,000
7. During this century, scientists expect many of the millions of such tanks around the world to
8. Determining the extent of a leak from a single underground tank can cost $25,000–250,000,
and cleanup costs range from $10,000 to more than $250,000. If the chemical reaches an
aquifer, effective cleanup is often not possible or is too costly.
G. Pollution prevention is the only effective way to protect groundwater.
2. Keep toxic chemicals out of the environment.
4. Require leak detectors on underground tanks.
6. Store harmful liquids in aboveground tanks with leak detection and collection systems.
H. There are many ways to purify drinking water.
1. Most of the more-developed countries have laws establishing drinking water standards. But
2. More-developed countries usually store surface water in a reservoir to increasing dissolved
3. Very pure groundwater or surface water sources need little treatment.
4. Protecting a water supply is usually a lot cheaper than building water purification plants.
5. We have the technology to convert sewer water into pure drinking water. But reclaiming
6. Simple measures can be used to purify drinking water:
a. Exposing a clear plastic bottle filled with contaminated water to intense sunlight can kill
7. SCIENCE FOCUS: Is Bottled Water a Good Option?
a. The United States has some of the world’s cleanest drinking water. Municipal water
systems in the United States are required to test their water regularly for a number of
pollutants and to make the results available to citizens.
b. About half of all Americans worry about getting sick from tap water contaminants, and
Chapter 11: Water Resources and Water Pollution
g. Health officials suggest that, before drinking expensive bottled water or buying costly
home water purifiers, consumers have their water tested by local health departments or
private labs (but not by companies trying to sell water purification equipment).
I. Ocean pollution is a growing and poorly understood problem.
1. The oceans hold 97% of the earth’s water, make up 97% of the biosphere where life is found,
and contain the planet’s greatest diversity and abundance of life.
2. Oceans help to provide and recycle the planet’s freshwater through the water cycle. They also
3. Coastal areas—especially wetlands, estuaries, coral reefs, and mangrove swamps—bear the
brunt of our enormous inputs of pollutants and wastes into the ocean.
a. 80-90% of municipal sewage from most coastal areas of less-developed countries, and in
4. CASE STUDY: Ocean Garbage Patches: There is No Away
a. SCIENCE FOCUS: Oxygen Depletion in the Northern Gulf of Mexico
b. The Great Pacific Garbage Patch is two gigantic masses of plastic and other solid wastes
in the middle of the North Pacific Ocean, trapped there by ocean currents.
5. SCIENCE FOCUS: Oxygen Depletion in the Northern Gulf of Mexico
a. The world’s third largest oxygen-depleted zone forms each year in the Gulf of Mexico as
a result of oxygen-depleting algal blooms caused primarily by high inputs of nutrients
from the Mississippi River basin.
b. The low oxygen levels suffocate fish, crabs, and shrimp that cannot move to less polluted
areas. Thus, these oxygen-depleted zones threaten aquatic biodiversity and whole
ecosystems.
c. Because of the size and agricultural importance of the Mississippi River basin, there are
no easy solutions to the problem of severe cultural eutrophication of this and other
overfertilized coastal zones around the world.
d. Preventive measures include:
i. applying less fertilizer on farms upstream, injecting fertilizer below the soil
Instructor’s Manual for Environmental Science, 15th edition
J. Ocean Pollution from Oil
a. Crude and refined petroleum reach the ocean from a number of sources and become highly
disruptive pollutants.
i. Visible sources are tanker accidents and blowouts at offshore oil drilling rigs, such as
that of the BP Deep Horizon rig in the Gulf of Mexico in 2010.
ii. The largest source of ocean oil pollution is urban and industrial runoff from land,
much of it from leaks in pipelines and oil-handling facilities. At least 37% of the oil
reaching the oceans is waste oil, dumped, spilled, or leaked onto the land or into
sewers by cities and industries, as well as by people changing their own motor oil.
b. Different components of petroleum are harmful to wildlife.
i. Volatile organic hydrocarbons in oil and other petroleum products kill many aquatic
organisms immediately upon contact.
c. Populations of many forms of marine life can recover from exposure to large amounts of
crude oil in warm waters with fairly rapid currents within about 3 years. But in cold and calm
waters, full recovery can take decades.
d. Recovery from exposure to refined oil, especially in estuaries and salt marshes, can take 10–
spillage of even the smallest amounts of oil.
K. Reducing ocean water pollution.
a. The key to protecting the oceans is to reduce the flow of pollution from land and air and from
streams emptying into these waters.
waters.
L. Reducing surface water pollution from nonpoint sources.
1. There are a number of ways to reduce nonpoint-source water pollution, most of which comes
from agriculture.
a. Reduce soil erosion by keeping cropland covered with vegetation.
Chapter 11: Water Resources and Water Pollution
M. Laws can help to reduce water pollution from point sources.
1. The Federal Water Pollution Control Act of 1972 (renamed the Clean Water Act) and the
1987 Water Quality Act form the basis of U.S. efforts to control pollution of the country’s
2. The EPA has been experimenting with a discharge trading policy, which uses market forces to
reduce water pollution in the United States.
3. According to the EPA, the Clean Water Act of 1972 led to numerous improvements in U.S.
water quality. Between 1992 and 2002:
4. More work to be done:
a. In 2006, the EPA found that 45% of the country’s lakes and 40% of the streams surveyed
were still too polluted for swimming or fishing, and that runoff of animal wastes from
5. Suggested improvements to the Clean Water Act include:
a. Shifting the focus of the law to water pollution prevention instead of focusing mostly on
end-of-pipe removal of specific pollutants.
b. Greatly increased monitoring for violations of the law.
N. Sewage treatment reduces water pollution.
1. About one-fourth of all homes in the United States are served by septic tanks.
a. Household sewage and wastewater is pumped into a settling tank.
2. In urban areas most waterborne wastes flow through a network of sewer pipes to wastewater
or sewage treatment plants.
Instructor’s Manual for Environmental Science, 15th edition
a. The first is primary sewage treatment: a physical process that uses screens and a grit tank,
then a primary settling tank where suspended solids settle out as sludge.
b. A second level is secondary sewage treatment where a biological process takes place in
which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen-
demanding, organic wastes.
c. A combination of primary and secondary treatment removes 95–97% of the suspended
solids and oxygen-demanding organic wastes, 70% of most toxic metal compounds and
nonpersistent synthetic organic chemicals, 70% of the phosphorus, and 50% of the
O. We can improve conventional sewage treatment.
1. Prevent toxic and hazardous chemicals from reaching sewage treatment plants and thus from
getting into sludge and water discharged from such plants.
a. Require industries and businesses to remove toxic and hazardous wastes from water sent
to municipal sewage treatment plants.
b. Encourage industries to reduce or eliminate use and waste of toxic chemicals.
c. Eliminate sewage outputs by switching to waterless, odorless composting toilet systems,
to be installed, maintained, and managed by professionals.
i. This process returns plant nutrients in human waste to the soil and thus
mimics the natural chemical cycling principle of sustainability.
P. SCIENCE FOCUS: Treating Sewage by Working with Nature.
a. Biologist John Todd has developed an ecological approach to treating sewage, which he calls
living machines.
i. This natural purification process uses passive solar energy, an artificial marsh and
complex series of organisms to filter and purify sewage.
Q. There are sustainable ways to reduce and prevent water pollution.
1. Most developed countries have enacted laws and regulations that have significantly reduced
2. To environmental and health scientists, the next step is to increase efforts to reduce and
prevent water pollution in both more- and less-developed countries, beginning with the
question: How can we avoid producing water pollutants in the first place?
3. This shift will require that citizens put political pressure on elected officials and also take
4. This chapter’s three big ideas:
a. One of the major global environmental problems is the growing shortage of freshwater in
many parts of the world.
R. Some areas get too much water from flooding.
1. Some areas sometimes have too much water because of natural flooding by streams, caused
mostly by heavy rain or rapidly melting snow.
3. Floodplains, which usually include highly productive wetlands, help to provide natural flood
and erosion control, maintain high water quality, and recharge groundwater.
5. To reduce the threat of flooding for people who live on floodplains:
6. Floods provide several benefits.
a. Create the world’s most productive farmland by depositing nutrient-rich silt on
7. Since the 1960s, human activities have contributed to a sharp rise in flood deaths and
damages, meaning that such disasters are partly human-made.
a. Removal of water-absorbing vegetation, especially on hillsides, which can increase
8. CONNECTIONS: Deforestation and Flooding in China.
a. In 1998, severe flooding in China’s Yangtze River watershed, home to 400 million
9. CASE STUDY: Living Dangerously on Floodplains in Bangladesh.
a. Bangladesh is one of the world’s most densely populated countries, with 184 million
people in 2010 living only slightly above sea level.
S. We can reduce flood risks.
1. To improve flood control, we can rely less on engineering devices such as dams and levees
and more on nature’s systems such as wetlands and natural vegetation in watersheds.
2. Straightening and deepening streams (channelization) reduces upstream flooding, but:
a. It eliminates aquatic habitats, reduces groundwater discharge, and results in a faster flow,
3. Levees or floodwalls along the sides of streams contain and speed up stream flow, but they
increase the water’s capacity for doing damage downstream.
4. Dams can reduce the threat of flooding by storing water in a reservoir and releasing it
gradually, but they also have a number of disadvantages.
5. An important way to reduce flooding is to preserve existing wetlands and restore degraded
wetlands to take advantage of the natural flood control they provide in floodplains.
6. We can sharply reduce emissions of greenhouse gases that contribute to projected climate
7. We can think carefully about where we choose to live. Many poor people live in flood-prone
areas because they have nowhere else to go. Most people, however, can choose not to live in
areas especially subject to flooding or to water shortages
Objectives
11-1 Will we have enough usable water?
CONCEPT 11-1A We are using available freshwater unsustainably by extracting it faster than nature and
replace it, and by wasting, polluting and underpricing this irreplaceable natural resource.
CONCEPT 11-1B Freshwater supplies are not evenly distributed, and one of every nine people on the
planet does not have adequate access to clean water.
2. Briefly describe Earth’s water supply and the role of the hydrological cycle. Define groundwater,
3. Define surface water, runoff, watershed/drainage basin, and reliable surface runoff. Emphasize
4. Define water footprint, virtual water and describe virtual water trading.
11-2 How can we increase freshwater supplies?
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 Large dam-and-reservoir systems and water transfer projects have greatly expanded water
supplies in some areas, but have also 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.
1. Assess the environmental effects of groundwater overpumping in order to increase water supplies.
2. Define desalination, and list the common desalination methods. Note the disadvantages and
11-3 How can we use freshwater more sustainably?
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 freshwater.
1. Discuss water waste. List the major reasons for this issue. List the common solutions for reducing
11-4 How can we deal with water pollution?
CONCEPT 11-4 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.
1. Define water pollution, and point source and nonpoint source varieties. Note the five major
sources of water pollution. Discuss the status of stream, lake, and reservoir pollution. Define
2. Emphasize why coastal areas of the oceans are more polluted than the open oceans. Discuss
prevention and source reduction strategies as the best way to reduce water pollution. Emphasize
that the U.S. has reduced water pollution from point sources. Note that sewage treatment in more-
developed countries has helped reduce nonpoint water pollution. Outline the controversy over
strengthening the Clean Water Act in the U.S.
Key Terms
aquifer
cultural eutrophication
dam
desalination
drainage basin
point sources
primary sewage treatment
reliable surface runoff
reservoir
secondary sewage treatment
virtual water
wastewater
water footprint
water pollution
water table
Teaching Tips
Instructors could introduce this topic by asking students to measure by volume how much water they waste
every morning when they brush their teeth, depending on how they brush their teeth.
• Those who waste the most of this precious resource leave the tap open as they are in the brushing act.
• Others shut the tap off as they brush their teeth.
• Ask the students to complete a 24-hour personal water usage audit—give them a guide with the typical
water usage.
• Enquire whether any of your students come from water-poor countries. How do they traditionally treat
freshwater resources?
• How good is your drinking water?
Instructor’s Manual for Environmental Science, 15th edition
Discussion Topics
1. How does water become polluted? Find a few actual examples of the following: animal feedlot wastes;
2. What was the sequence of events in one of the text case studies or a local example of water pollution?
3. What is the history of the human water supply? Include the following components: drought history of the
4. How responsible are upstream communities for ensuring that high-quality water is delivered to downstream
communities? Will water wars increase in the next 50 years? Be sure to include: deep aquifer research
5. How has the Safe Drinking Water Act of 1974, the Clean Water Act, local and state regulations, the
Environmental Protection Agency, and the Toxic Substances Control Act played a role in water quality
management?
6. What are some of the challenges with the global management of a shared resource, water? Who are the
political players in this challenge?
Activities and Projects
1. Ask your class to determine the local agricultural and industrial uses of water. Is irrigation used widely?
What is the source of irrigation water? What water conservation practices are used by local government,
industry, and agriculture?
3. Invite a local, state, or federal water pollution control official to discuss water pollution control methods,
progress, and problems with your class.
4. Visit a sewage treatment plant with your class. Find out what level of sewage treatment is used in your
community. What is the volume of effluent discharged? If effluent is discharged into a river or stream, is
the water subsequently used for drinking water supply? Are there bodies of water in your locale unfit for
fishing or swimming because of inadequately treated sewage effluent? If so, is anything being done to
correct the problem?
6. Have your students explore community water resources. Where does your town get its water? What is the
average daily use in summer? In winter? What are the major uses in your area? (List the 10 biggest users.)
How much does your class use?
