Ch11 - Water Resources

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
* Understand basic surface water and groundwater processes
* Be able to discuss some of the key principles associated with water management
* Know what wetlands are and understand their environmental significance
* Know why we are facing a global water shortage linked to food supply

Chapter 11 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 sections reveal surface water processes and groundwater processes, as well as the interactions between surface water and groundwater systems. Following a brief section on desalination, the chapter closes with sections on the types of and trends in water use, on water management, on the effects of water development on ecosystems, and on emerging water shortages around the globe.

Chapter 11 Outline
I. Water: A brief global perspective
A. The global water cycle
1. movement or transfer from one of Earth’s storage compartments to another
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
2. residence time varies depending upon location
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
2. watersheds/drainage basins
3. large drainage basins consist of smaller ones
B. Factors affecting runoff and sediment yield
1. geologic factors
2. topographic factors
3. climatic factors
4. vegetation factors
5. land-use factors
III. Groundwater
A. Groundwater zones
1. major source of groundwater is infiltrated precipitation
2. vadose zone
3. zone of saturation
4. water table
B. Aquifers
1. aquifer
2. confining layer
3. unconfined aquifer
4. perched aquifer
5. confined/artesian aquifer
6. groundwater recharge
7. groundwater discharge
8. cone of depression
C. Groundwater movement
1. hydraulic gradient
2. hydraulic conductivity and porosity
3. Darcy’s Law
D. Groundwater supply
1. nearly half of U.S. population uses groundwater as primary drinking water source
2. total amount of groundwater in U.S. is enormous
3. cost of water pumping and exploration reduces total quantity of available groundwater
4. groundwater mining, e.g., Ogallala aquifer
IV. Interactions between surface water and groundwater
A. Surface water and groundwater
1. considered parts of the same resource
2. nearly all surface water environments have strong linkages with groundwater
3. effluent versus influent streams
4. karst
a. karst topography causes many environmental problems
1) water pollution sources
2) collapse
3) groundwater mining
V. Desalination
A. An expensive form of water treatment
1. practiced at several hundred plants around the world
2. expense precludes use except when alternative sources are not available
VI. Water use
A. Types of water use
1. offstream
2. consumptive
3. instream
B. Movement of water to people
1. water is often moved vast distances from areas with abundant rainfall to areas of high usage
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
4. use of water in urban and rural sectors increased from 1960–1995
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
1. agriculture
2. domestic
3. thermoelectricity
VII. Water management in the future
A. Managing water resources is complex and will become more difficult as demand increases
1. see A Closer Look: Management of the Colorado River
2. cities in need of water are beginning to treat it as a valuable commodity
3. new philosophy of water management is needed
VIII. Water and ecosystems
A. Major ecosystems of the world
1. evolved in response to climate, nutrients, soils, and hydrology
2. changes in those factors affect ecosystems
B. Water resources development, especially dam, reservoir, and canal construction, has a variety of environmental impacts
1. land is lost in areas flooded by reservoirs
2. reservoir traps sediment, which cannot feed systems downstream
3. hydrology and sediment transport systems downstream of a dam change the environment and organisms
IX. Emerging global water shortages
A. Isolated shortages of water indicate global pattern of depleting resource
1. groundwater depletion
2. desiccation of large lakes
3. dramatic reduction in flow of large rivers in some years
B. Water demand has tripled in the past 50 years
1. correlates with tripling of grain production
2. as population increases rapidly, water shortages will be linked to food shortages
3. solution is to control human population growth and conserve water