Presentation Transcript

1. Chapter 14

   Water
2. 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
3. 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.
4. 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.
5. Forested Land Agricultural Crops Timber Stand Cattle Farming Residential Industrial Dam
6. Georgia’s Major Watersheds Do you see Atlanta?
7. Altamaha River Watershed
8. Ocmulgee Agricultural fields contribute to non-point source pollution Using GIS to determine land use in a watershed
9. 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
10. Artesian well
11. 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%).
12. Global Water Use
13. 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.
14. Stress on the World’s River Basins Comparison of the amount of water available with the amount used by humans. Figure 14-6
15. 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.
16. 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.
17. Light blue color indicates water – between the rocks and within the cracks of bedrock
18. What are ways we protect our water and what are ways we degrade our groundwater?
19. Why should we protect our mountains?
20. Groundwater Depletion: A Growing Problem Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest). Figure 14-8
21. Ogallala Aquifer World’s largest ancient aquifer
22. Excessive irrigation in the mid-west has depleted the Ogallala Aquifer faster than it can be replenished
23. Other Effects of Groundwater Overpumping Groundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater. Figure 14-11
24. Other Effects of Groundwater Overpumping Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater. Figure 14-10
25. 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
26. 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
27. 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.
28. Hoover Dam
29. 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
30. Powerlines Falling water spins the turbine connected to the generator to create energy Reservoir Dam Powerhouse Intake Turbine Fig. 14-13b, p. 317
31. Electricity turbines inside the Hoover Dam
32. 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).
33. 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
34. 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
35. 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
36. 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 is 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.
37. 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. Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.
38. Removal of this dam in Washington will restore salmon runs
39. 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.
40. 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
41. Satellite image: Colorado River Aqueduct
42. Colorado River Aqueduct
43. Case Study: The Aral Sea Disaster 1989 2001 The Aral Sea was once the world’s fourth largest freshwater lake. Figure 14-17
44. View from space The disappearance of the Aral Sea over time
45. The diversion of water from the Aral Sea has dried up the fishing industry
46. 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.
47. 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 salt in solid form. Reverse osmosis: uses high pressure to force saltwater through a membrane filter.
48. DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIES Seeding clouds with tiny particles of chemicals to increase rainfall towing icebergs or huge bags filled with freshwater to dry coastal areas have all been proposed but are unlikely to provide significant amounts of freshwater.
49. Iceberg Towing Source of freshwater
50. INCREASING WATER SUPPLIES BY WASTING LESS WATER We waste about two-thirds of the water we use, but we could cut this waste to 15%. 65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses. Water is underpriced through government subsidies. The lack of government subsidies for improving the efficiency of water use contributes to water waste.
51. INCREASING WATER SUPPLIES BY WASTING LESS WATER Sixty percent of the world’s irrigation water is currently wasted, but improved irrigation techniques could cut this waste to 5-20%. Center-pivot, low pressure sprinklers sprays water directly onto crop. It allows 80% of water to reach crop. Has reduced depletion of Ogallala aquifer in Texas High Plains by 30%.
52. Drip irrigation (efficiency 90–95%) Gravity flow (efficiency 60% and 80% with surge valves) Center pivot (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually comes from an aqueduct system or a nearby river. Fig. 14-18, p. 325
53. Center-pivot irrigation
54. Drip irrigation
55. Gravity flow irrigation
56. Gravity flow irrigation
57. Sprinkler system loosing a great deal of water due to evaporation
58. Solutions Reducing Irrigation Water Waste • Line canals bringing water to irrigation ditches • Level fields with lasers • Irrigate at night to reduce evaporation • Monitor soil moisture to add water only when necessary • Polyculture • Organic farming • Don't grow water-thirsty crops in dry areas • Grow water-efficient crops using drought resistant and salt-tolerant crop varieties • Irrigate with treated urban waste water • Import water-intensive crops and meat Fig. 14-19, p. 326
59. Solutions: Getting More Water for Irrigation in Developing Countries – The Low-Tech Approach Many poor farmers in developing countries use low-tech methods to pump groundwater and make more efficient use of rainfall. Figure 14-20
60. Raising the Price of Water: A Key to Water Conservation We can reduce water use and waste by raising the price of water while providing low lifeline rates for the poor. When Boulder, Colorado introduced water meters, water use per person dropped by 40%. A 10% increase in water prices cuts domestic water use by 3-7%.
61. Solutions: Using Less Water to Remove Industrial and Household Wastes We can mimic the way nature deals with wastes instead of using large amounts of high-quality water to wash away and dilute industrial and animal wastes. Use nutrients in wastewater before treatment as soil fertilizer. Use waterless and odorless composting toilets that convert human fecal matter into a small amount of soil material. Waterless urinal
62. TOO MUCH WATER Heavy rainfall, rapid snowmelt, removal of vegetation, and destruction of wetlands cause flooding. Floodplains, which usually include highly productive wetlands, help provide natural flood and erosion control, maintain high water quality, and recharge groundwater. To minimize floods, rivers have been narrowed with levees and walls, and dammed to store water.
63. TOO MUCH WATER Comparison of St. Louis, Missouri under normal conditions (1988) and after severe flooding (1993). Figure 14-22
64. TOO MUCH WATER Human activities have contributed to flood deaths and damages. Figure 14-23
65. Solutions Reducing Flood Damage Prevention Control Preserve forests on watersheds Strengthen and deepen streams (channelization) Preserve and restore wetlands in floodplains Build levees or floodwalls along streams Tax all development on floodplains Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreation Build dams Fig. 14-24, p. 331
66. SOLUTIONS: USING WATER MORE SUSTAINABLY We can use water more sustainably by cutting waste, raising water prices, preserving forests and wetlands in water basins, and slowing population growth. Figure 14-25
67. What Can You Do? Water Use and Waste • Use water-saving toilets, showerheads, and faucet aerators. • Shower instead of taking baths, and take short showers. • Stop water leaks. • Turn off sink faucets while brushing teeth, shaving, or washing. • Flush toilets only when necessary. • Wash only full loads of clothes or use the lowest water-level for smaller loads. • Use recycled (gray) water for lawn, gardens, house plants, car washing. • Wash a car from a bucket of soapy water, and use the hose for rinsing only. • If you use a commercial car wash, try to find one that recycles its water. • Replace your lawn with native plants that need little if any watering and decorative gravel or rocks. • Water lawns and gardens in the early morning or evening. • Sweep or blow off driveways instead of hosing off with water. • Use drip irrigation and mulch for gardens and flowerbeds. Fig. 14-25, p. 333