Learning Objectives
After reading and studying this chapter, students should:
• Understand the water cycle and the basic concepts associated with our water
supply.
• Understand the main types of water use.
Chapter Summary
This chapter focuses on processes and challenges related to water resources. The opening
section discusses the global water cycle and the issue of water abundance. Subsequent
Chapter Outline
I. Water: A brief global perspective
A. The global water cycle
2. major processes are evaporation, precipitation, transpiration, surface runoff, and
groundwater flow
3. chemical and sediment load of surface water
B. Water as a resource
1. found in liquid, solid, or gaseous state on or near Earth surface
3. more than 99% of Earth’s water unavailable or unsuitable for human use
II. Surface water
A. Surface runoff and sediment yield
1. runoff affects erosion and transport of materials
3. large drainage basins consist of smaller ones
B. Factors affecting runoff and sediment yield
2. topographic factors
4. vegetation factors
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Water Resources
Water Resources
5. land-use factors
III. Groundwater
A. Groundwater zones
2. vadose zone
a. pollution passes through vadose zone en route to groundwater
4. water table
5. factors influencing rate of infiltration
a. topography
b. soil and rock type
B. Aquifers
2. confining layer
4. perched aquifer
6. groundwater recharge
8. cone of depression
C. Groundwater movement
2. hydraulic conductivity and porosity
D. Groundwater supply
1. nearly half of the United States population uses groundwater as primary drinking
water source
3. cost of water pumping and exploration reduces total quantity of available
groundwater
5. town and city water shortages in High Plains
IV. Interactions between surface water and groundwater
A. Surface water and groundwater
1. considered parts of the same resource
3. effluent versus influent streams
4. karst
a. karst topography includes sinkholes, karst plains, and cavern systems
b. karst topography causes many environmental problems
2) collapse
V. Desalination
A. An expensive form of water treatment
2. use will increase as water shortage increases
VI. Water use
A. Types of water use
1. offstream
3. instream
B. Movement of water to people
2. many large cities (e.g., Los Angeles, New York) must seek water from areas at
increasingly greater distances
C. Trends in water use
1. surface water withdrawals far exceed groundwater withdrawals in U.S.
2. water withdrawals in U.S. increased until 1980 and have since decreased
3. irrigation and thermoelectric users are the primary consumers
5. use of water by agriculture leveled off in 1980 and has slightly decreased
6. thermoelectric water use increased dramatically from 1960–1980, then decreased
7. since 1980, industry has used significantly less fresh water
D. Water conservation
2. domestic
3. thermoelectricity
E. Virtual water: Conservation of water at the global scale
1. the amount of water necessary to produce a product
3. consuming a crop influences and impacts the water resources of the country of
origin
5. water conservation at the global level is very important
6. advantages of virtual water
a. the promotion of efficient use of water from a local to a global scale
VII. Water management in the future
A. Managing water resources is complex and will become more difficult as demand
increases
2. cities in need of water are beginning to treat it as a valuable commodity
4. excesses and deficiencies in water are natural and can be planned for
VIII. Water and ecosystems
A. Major ecosystems of the world
1. evolved in response to climate, nutrients, soils, and hydrology
3. Water processes and quality are a factor in the continued existence of some
ecosystems (see A Closer Look: Wetlands)
B. Water resources development, especially dam, reservoir, and canal construction, has a
variety of environmental impacts
Water Resources
1. land is lost in areas flooded by reservoirs
3. hydrology and sediment transport systems downstream of a dam change the
environment and organisms (see A Closer Look: Management of the Colorado
River)
IX. Emerging global water shortages
A. Isolated shortages of water indicate global pattern of depleting resource
1. groundwater depletion
3. dramatic reduction in flow of large rivers in some years
B. Water demand has tripled in the past 50 years
2. as population increases rapidly, water shortages will be linked to food shortages
3. solution is to control human population growth and conserve water
Answers to Review Questions and Critical Thinking Questions
Review Questions
2. The water table separates the unsaturated vadose zone, which lies near Earth’s surface,
and the zone of saturation, where true groundwater flow occurs.
4. The major factors controlling the movement of groundwater are hydraulic gradient and
hydraulic conductivity.
6. Interactions between surface water and groundwater include the exchange of water
7. Instream water uses do not withdraw water from its source, while offstream uses remove
or divert the water from its source.
9. The biggest users of fresh water are agriculture and the thermoelectric industry.
11. Luna Leopold’s philosophy of water management is centered on the belief that
12. Wetlands are areas that are either inundated by water or the land is saturated for at least
Chapter 13 – Instructor’s Manual
Critical Thinking Questions
1. A wetlands inventory would require knowledge of the types of wetlands present in the
student’s region, as well as sources of information, such as public records or time
2. The background information for this task is summarized in the case history on the
Edwards Aquifer in this chapter. A response to this task should address the conflicts
3. A response to this question will reflect the student’s opinion, but should focus on the link