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Chapter 14

Chapter 14. Water. Chapter Overview Questions. Why is water so important, how much freshwater is available to us, and how much of it are we using? What causes freshwater shortages, and what can be done about this problem? What are the advantages and disadvantages of withdrawing groundwater?

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Chapter 14

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  1. Chapter 14 Water

  2. Chapter Overview Questions • Why is water so important, how much freshwater is available to us, and how much of it are we using? • What causes freshwater shortages, and what can be done about this problem? • What are the advantages and disadvantages of withdrawing groundwater? • What are the advantages and disadvantages of using dams and reservoirs to supply more water?

  3. Chapter Overview Questions (cont’d) • What are the advantages and disadvantages of transferring large amounts of water from one place to another? • Can removing salt from seawater solve our water supply problems? • How can we waste less water? • How can we use the earth’s water more sustainably? • What causes flooding, and what can we do about it?

  4. Updates Online The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles. • InfoTrac: For money or for life. Jeff Conant. Earth Island Journal, Autumn 2006 v21 i3 p33(6). • InfoTrac: Backstory: Tapping the world. The Christian Science Monitor March 22, 2006 p20. • InfoTrac: A water crisis in the making. Christopher Meyer. Middle East Economic Digest, April 7, 2006 v50 i14 p47(2). • Science Daily: Historic Colorado River Streamflows Reconstructed Back To 1490 • National Geographic: Map: Middle East Natural Resources • Science Daily: Putting Coal Ash Back Into Mines A Viable Option For Disposal, But Risks Must Be Addressed

  5. Video: Western Drought • This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

  6. Core Case Study: Water Conflicts in the Middle East - A Preview of the Future • Many countries in the Middle East, which has one of the world’s highest population growth rates, face water shortages. Figure 14-1

  7. Water Conflicts in the Middle East: A Preview of the Future • Most water in this dry region comes from the Nile, Jordan or Tigris rivers. • Countries are in disagreement as to who has water rights. • Currently, there are no cooperative agreements for use of 158 of the world’s 263 water basins that are shared by two or more countries.

  8. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle. • Only about 0.02% of the earth’s water supply is available to us as liquid freshwater.

  9. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • Comparison of population sizes and shares of the world’s freshwater among the continents. Figure 14-2

  10. Percent of world's water resources and population Continent 36% Asia 60.5% 10% Africa 14% 8% Europe 11.3% 15% North and Central America 7.3% 26% South America and Caribbean 6.4% 5% Oceania 0.5% Fig. 14-2, p. 307

  11. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • Some precipitation infiltrates the ground and is stored in soil and rock (groundwater). • Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water. • The land from which the surface water drains into a body of water is called its watershed or drainage basin.

  12. Unconfined Aquifer Recharge Area Evaporation and transpiration Evaporation Precipitation Confined Recharge Area Runoff Flowing artesian well Recharge Unconfined Aquifer Stream Well requiring a pump Water table Infiltration Lake Infiltration Unconfined aquifer Less permeable material such as clay Confined aquifer Confining impermeable rock layer Fig. 14-3, p. 308

  13. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • We currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by 2025. • About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources. • Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).

  14. Water in the United States • Average precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom). Figure 14-4

  15. Average annual precipitation (centimeters) Less than 41 81–122 41–81 More than 122 Fig. 14-4a, p. 309

  16. Acute shortage Shortage Adequate supply Metropolitan regions with population greater than 1 million Fig. 14-4b, p. 309

  17. Case Study: Freshwater Resources in the United States • 17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife. Figure 14-5

  18. Wash. N.D. Montana Oregon Idaho S.D. Wyoming Nevada Neb. Utah Kansas Colo. California Oak. N.M. Texas Highly likely conflict potential Substantial conflict potential Moderate conflict potential Unmet rural water needs Fig. 14-5, p. 310

  19. TOO LITTLE FRESHWATER • About 41% of the world’s population lives in river basins that do not have enough freshwater. • Many parts of the world are experiencing: • Rivers running dry. • Lakes and seas shrinking. • Falling water tables from overpumped aquifers.

  20. Stress on the World’s River Basins • Comparison of the amount of water available with the amount used by humans. Figure 14-6

  21. Europe North America Asia Africa South America Australia Stress High None Fig. 14-6, p. 311

  22. Case Study: Who Should Own and Manage Freshwater Resources • There is controversy over whether water supplies should be owned and managed by governments or by private corporations. • European-based water companies aim to control 70% of the U.S. water supply by buying up water companies and entering into agreements with cities to manage water supplies.

  23. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Should private companies own or manage most of the world's water resources? • a. No. Democratically elected governments, which are accountable to the voters, should own and manage water resources. • b. Qualified yes. Governments should own the water, but expert private companies should manage it. • c. Depends. Each case must be decided independently. The record on private versus public ownership is mixed. • d. Yes. Private companies have more expertise and experience in managing water resources than most government bureaucrats.

  24. TOO LITTLE FRESHWATER • Cities are outbidding farmers for water supplies from rivers and aquifers. • Countries are importing grain as a way to reduce their water use. • More crops are being used to produce biofuels. • Our water options are: • Get more water from aquifers and rivers, desalinate ocean water, waste less water.

  25. WITHDRAWING GROUNDWATER TO INCREASE SUPPLIES • Most aquifers are renewable resources unless water is removed faster than it is replenished or if they are contaminated. • Groundwater depletion is a growing problem mostly from irrigation. • At least one-fourth of the farms in India are being irrigated from overpumped aquifers.

  26. Trade-Offs Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Sinking of land (subsidence) from overpumping Available year-round Exists almost everywhere Polluted aquifers for decades or centuries Renewable if not overpumped or contaminated Saltwater intrusion into drinking water supplies near coastal areas Reduced water flows into surface waters No evaporation losses Increased cost and contamination from deeper wells Cheaper to extract than most surface waters Fig. 14-7, p. 313

  27. Groundwater Depletion: A Growing Problem • The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest). • Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. Figure 14-8

  28. Groundwater Overdrafts: High Moderate Minor or none Fig. 14-8, p. 314

  29. Other Effects of Groundwater Overpumping • Groundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater. Figure 14-11

  30. Major irrigation well Well contaminated with saltwater Water table Sea level Fresh groundwater aquifer Saltwater Seafloor Interface Saltwater intrusion Interface Normal interface Fig. 14-11, p. 315

  31. Other Effects of Groundwater Overpumping • Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater. Figure 14-10

  32. Groundwater Pumping in Saudi Arabia (1986 – 2004) • Irrigation systems from the nonrenewable aquifer appear as green dots. Brown dots are wells that have gone dry. Figure 14-9

  33. Solutions Groundwater Depletion Prevention Control Raise price of water to discourage waste Waste less water Subsidize water conservation Ban new wells in aquifers near surface waters Tax water pumped from wells near surface waters Buy and retire groundwater withdrawal rights in critical areas Set and enforce minimum stream flow levels Do not grow water-intensive crops in dry areas Fig. 14-12, p. 316

  34. USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER • Large dams and reservoirs can produce cheap electricity, reduce downstream flooding, and provide year-round water for irrigating cropland, but they also displace people and disrupt aquatic systems.

  35. Figure 14-13

  36. Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Risk of failure and devastating downstream flooding Can produce cheap electricity (hydropower) Downstream flooding is reduced Migration and spawning of some fish are disrupted Fig. 14-13a, p. 317

  37. Powerlines Reservoir Dam Powerhouse Intake Turbine Fig. 14-13b, p. 317

  38. Case Study: The Colorado Basin – an Overtapped Resource • The Colorado River has so many dams and withdrawals that it often does not reach the ocean. • 14 major dams and reservoirs, and canals. • Water is mostly used in desert area of the U.S. • Provides electricity from hydroelectric plants for 30 million people (1/10th of the U.S. population).

  39. Case Study: The Colorado Basin – an Overtapped Resource • Lake Powell, is the second largest reservoir in the U.S. • It hosts one of the hydroelectric plants located on the Colorado River. Figure 14-15

  40. The Colorado River Basin • The area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states. Figure 14-14

  41. IDAHO WYOMING Dam Aqueduct or canal Salt Lake City Upper Basin Denver Grand Junction Lower Basin UPPER BASIN UTAH Colorado River NEVADA Lake Powell COLORADO Grand Canyon Glen Canyon Dam Las Vegas NEW MEXICO Boulder City CALIFORNIA Los Angeles ARIZONA Albuquerque LOWER BASIN Palm Springs 0 100 mi. Phoenix San Diego Yuma 0 150 km Tucson Mexicali All-American Canal MEXICO Gulf of California Fig. 14-14, p. 318

  42. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. • Do the advantages of large dams outweigh their disadvantages? • a. No. Large dams inflict extensive environmental damage and humans must learn to meet their needs without them. • b. Yes. Dams are critical in providing water and electricity for people, especially in developing countries.

  43. Case Study: China’s Three Gorges Dam • There is a debate over whether the advantages of the world’s largest dam and reservoir will outweigh its disadvantages. • The dam will be 2 kilometers long. • The electric output will be that of 18 large coal-burning or nuclear power plants. • It will facilitate ship travel reducing transportation costs. • Dam will displace 1.2 million people. • Dam is built over seismatic fault and already has small cracks.

  44. Dam Removal • Some dams are being removed for ecological reasons and because they have outlived their usefulness. • In 1998 the U.S. Army Corps of Engineers announced that it would no longer build large dams and diversion projects in the U.S. • The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams. • Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.

  45. TRANSFERRING WATER FROM ONE PLACE TO ANOTHER • Transferring water can make unproductive areas more productive but can cause environmental harm. • Promotes investment, jobs and strong economy. • It encourages unsustainable use of water in areas water is not naturally supplied.

  46. Case Study: The California Experience • A massive transfer of water from water-rich northern California to water-poor southern California is controversial. Figure 14-16

  47. CALIFORNIA NEVADA Shasta Lake UTAH Sacramento River Oroville Dam and Reservoir Feather River North Bay Aqueduct Lake Tahoe Sacramento San Francisco Hoover Dam and Reservoir (Lake Mead) South Bay Aqueduct Fresno San Joaquin Valley San Luis Dam and Reservoir Colorado River Los Angeles Aqueduct ARIZONA California Aqueduct Colorado River Aqueduct Central Arizona Project Santa Barbara Los Angeles Salton Sea San Diego Phoenix Tucson MEXICO Fig. 14-16, p. 321

  48. Case Study: The Aral Sea Disaster • The Aral Sea was once the world’s fourth largest freshwater lake. Figure 14-17

  49. Case Study: The Aral Sea Disaster • Diverting water from the Aral Sea and its two feeder rivers mostly for irrigation has created a major ecological, economic, and health disaster. • About 85% of the wetlands have been eliminated and roughly 50% of the local bird and mammal species have disappeared. • Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

  50. DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIES • Removing salt from seawater by current methods is expensive and produces large amounts of salty wastewater that must be disposed of safely. • Distillation: heating saltwater until it evaporates, leaves behind water in solid form. • Reverse osmosis: uses high pressure to force saltwater through a membrane filter.

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