Chapter Summary: Chapter 8
Water Resources and Water Pollution
8-1 Will we have enough usable water?
The management of the world’s water supply is a huge 21 st century challenge. Water is not equally available around
the world; the location of the water, the type of water, and the demand for it all stress available water supplies.
CONCEPT 8-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little
for this irreplaceable natural resource. CONCEPT 8-1B One of every six people does not have sufficient access to
clean water, and this situation will almost certainly get worse.
1. Briefly describe the earth's water supply and its distribution. How does water flow through the
hydrologic cycle? How does human activity interfere with the hydrologic cycle?
2. How much of the world's reliable runoff do we use? What impact will predicted population increases
have on our water use? Describe two areas in the world with significant water scarcity.
8-2 How can we increase water supplies?
Water supplies can be increased by building dams, transferring water from high water areas to low water areas,
withdrawing groundwater, and desalination. CONCEPT 8-2 Pumping groundwater, building dams, transferring
water, and desalination can all increase water supplies, but these strategies all create environmental problems.
3. Briefly describe three major water problems. Evaluate which of these problems is of most concern in
the United States and in the region in which you live.
4. Evaluate increasing the water supply through use of dams and water transfer projects. Compare the
advantages and disadvantages of increasing the water supply through use of groundwater, desalination,
and water transfer.
8-3 How can we use water more sustainably?
A blue revolution must take place in order to conserve water; two-thirds of the water that we have available is
wasted through evaporation, leaks, overuse in irrigation, etc. CONCEPT 8-3 We can use water more sustainability
by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other
ecosystems that store and release water.
5. State how much water is wasted. Briefly describe measures that can be taken to reduce water losses
through irrigation, industry, and home use.
6. What is one significant change you can make to conserve water? What would be the impact of
increasing the cost of water on water use?
8-4 How can we reduce the threat of flooding?
Natural flooding by streams produces rich floodplains and recharges groundwater supplies. Increased human
activities in active floodplains have contributed to the significant damage and destruction that result from floods.
Concept 8-4 We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds
and by not building in areas subject to frequent flooding.
7. What are the factors that have led to flooding disasters in Bangladesh?
8. Describe ways to mitigate flood risks. What inherent risks are present in those approaches to flood
control?
8-5 What are the causes and effects of water pollution?
Both single sources and dispersed sources contribute to water pollution. Dispersed (nonpoint) sources are the most
difficult to control. CONCEPT 8-5 Water pollution, primarily caused by agricultural activities, industrial facilities,
and mining, and worsened by population growth and resource use, causes illness and death in humans and other
species, and disrupts ecosystems.
9. List eight common types of water pollutants and give an example of each. Distinguish between point
and nonpoint sources of pollution.
10. How many people lack access to clean drinking water in the world? What is the impact of
contaminated drinking water?
8-6 What are the major water pollution problems in streams and lakes?
The ability of streams and lakes to naturally recover from pollution depends primarily on flow rate and the type of
pollutant. CONCEPT 8-6 Addition of pollutants and excessive nutrients to streams and lakes can disrupt these
ecosystems, and prevention of such pollution is more effective and less costly than cleaning it up.
11. Draw an oxygen sag curve to illustrate what happens to dissolved oxygen levels in streams below
points where degradable oxygen-demanding wastes are added.
12. Compare problems of lake water pollution to those of stream pollution. List three ways to prevent
cultural eutrophication and three ways to clean up cultural eutrophication. Summarize the state of the
Great Lakes.
8-7 What are the major pollution problems affecting groundwater and other drinking water sources?
The properties of groundwater (location, flow rate, temperature, etc.) make it extremely difficult to detect sources of
pollutants or clean them up if it becomes contaminated. Bottled water has a significantly higher monetary and
environmental cost without the assurances of cleaner water. CONCEPT 8-7 Chemicals used in agriculture, industry,
transportation, and homes can spill and leak into groundwater and make it undrinkable; while we can purify polluted
water, protecting it through pollution prevention is the least expensive and most effective strategy.
13. List the major pollutants of groundwater and three ways to control groundwater pollution.
14. Summarize ways to purify drinking water.
8-8 What are the major water pollution problems affecting oceans?
Much of the world's population lives on the coast, and with that comes significant pollution. As populations rise,
ocean pollution may increase significantly with increased human activity. CONCEPT 8-8 The great majority of
ocean pollution originates on land and includes oil and other toxic chemicals and solid waste, which threaten fish
and wildlife, and disrupt marine ecosystems; the key to protecting oceans is to reduce the flow of pollutants into
coastal waters.
15. Compare freshwater pollution to ocean pollution. List three ways to protect coastal waters.
8-9 How can we best deal with water pollution?
Many of the regulations that have reduced point-source pollution in developed countries (like the U.S.) were largely
the result of bottom-up political pressure. The most important next step in controlling water pollution is to minimize
it or prevent it altogether. Developing countries, in particular, need specific assistance to shift to pollution
prevention. CONCEPT 8-9 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.
16. Briefly describe two major laws that protect water quality in the United States. Outline the arguments
for and against strengthening the Clean Water Act.
17. Briefly describe and distinguish among septic tanks, primary, secondary, and advanced sewage
treatment. Describe biologist John Todd's approach to sewage treatment.