Presentation on theme: "Chapter 14 Water Water. Chapter Overview Questions Why is water so important, how much freshwater is available to us, and how much of it are we using?"— Presentation transcript:
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?
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?
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
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.
Nile River- 97% of Egypt’s freshwater 97% of Egypt’s freshwater Shared by Ethiopia, Sudan, & Egypt Shared by Ethiopia, Sudan, & Egypt
Jordan River- Shared by Syria, Jordan, Palestine (Gaza & West Bank), & Israel Syria pop. will double by 2050 Syria plans to build dams and withdraw more water Israel does cooperate with Jordan & Palestine
Water Conflicts in the Middle East? Tigris & Euphrates Rivers- Shared by Turkey, Syria, & Iraq.
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 0.024% of the earth’s water supply is available to us as liquid freshwater.
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL Comparison of population sizes and shares of the world’s freshwater among the continents. Figure 14-2
Fig. 14-2, p. 307 Continent Percent of world's water resources and population Asia 60.5% 36% Africa 10% 8% Europe North and Central America 7.3% South America and Caribbean 6.4% 26% 15% 5% Oceania 11.3% 0.5% 14%
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. The land from which the surface water drains into a body of water is called its watershed or drainage basin.
Ground Water A simplified surficial aquifer Coastal Georgia: -a few feet down -“sulfur water” Zone of saturation Water Table
Fig. 14-3, p. 308 Unconfined Aquifer Recharge Area Precipitation Evaporation and transpirationEvaporation Confined Recharge Area Runoff Flowing artesian well Recharge Unconfined Aquifer Stream Well requiring a pump Infiltration Water table Lake Infiltration Unconfined aquifer Confined aquifer Confining impermeable rock layer Less permeable material such as clay
Ground Water: Artesian Wells Bogue Chitto River, LA Jasper, SC
Ground Water: Artesian Wells ga.water.usgs.gov/edu/gwartesian.html The diagram below shows the aquifer system near Brunswick, Georgia, as it was before development of the Floridan aquifer system in the 1880’s. The aquifer system was under artesian conditions and the pressure in the aquifer system was great enough that wells flowed at land surface throughout most of the coastal area. In some areas, pressure was high enough to elevate water to multi-story buildings without pumping. The artesian water level (potentiometric surface) was about 65 feet above sea level at Brunswick. Ground water discharged naturally to springs, rivers, ponds, wetlands, and other surface- water bodies and to the Atlantic Ocean. Nowadays, ground- water pumping has caused the water level in the aquifer to decline throughout the entire coastal area, with the result that some artesian aquifers no longer have enough pressure to cause a well to naturally flow to the land surface.the water level in the aquifer to decline
Ground Water: Overpumping (overdrafting) Note: The Floridan Aquifer (500-600 feet below Brunswick) has two saltwater intrusion plumes, one from the ocean and one from an ancient saltwater aquifer that underlies it (not shown in the diagram)
Ground Water: Artesian Wells During October 2002, the Durango Paper Company (formerly Gillman Paper Company) in St. Marys, Georgia, shutdown paper-mill operations; the shutdown resulted in decreased ground-water withdrawal in Camden County by 35.6 million gallons per day. The decrease in withdrawal resulted in water-level rise in wells completed in the Floridan aquifer system and the overlying surficial and Brunswick aquifer systems; many wells in the St. Marys area flowed for the first time since the mill began operations during 1941. pubs.usgs.gov/sir/2004/5295/
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%).
Water in the United States Average precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom). Next
Fig. 14-4a, p. 309 Average annual precipitation (centimeters) More than 122 Less than 4181–122 41–81
Fig. 14-4b, p. 309 Acute shortage Metropolitan regions with population greater than 1 million Shortage Adequate supply
Case Study: Freshwater Resources in the United States 17 western states by 2025 could face intense conflict over scarce water needed for Urban growth Urban growth Irrigation Irrigation Recreation Recreation Wildlife. Wildlife. Figure 14-5
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. Rivers running dry. Lakes and seas shrinking. Lakes and seas shrinking. Falling water tables from overpumped aquifers. Falling water tables from overpumped aquifers.
Stress on the World’s River Basins Comparison of the amount of water available with the amount used by humans. Figure 14-6
Fig. 14-6, p. 311 Europe North America Asia Africa South America Australia Stress HighNone Water available vs water used
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. Two large French companies (Veolia & Suez) 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.
How Would You Vote? 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. The profit motive is too high to trust these companies. a. No. Democratically elected governments, which are accountable to the voters, should own and manage water resources. The profit motive is too high to trust these companies. b. Qualified yes. Governments should own the water, but expert private companies should manage it. 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. 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. d. Yes. Private companies have more expertise and experience in managing water resources than most government bureaucrats.
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. Get more water from aquifers and rivers, desalinate ocean water, waste less water.
TOO LITTLE FRESHWATER Our water options are: Get more water from aquifers, rivers, & lakes Get more water from aquifers, rivers, & lakes Desalinate ocean water Desalinate ocean water Waste less water. Waste less water.
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. At least one-fourth of the farms in India are being irrigated from overpumped aquifers.
Fig. 14-7, p. 313 Trade-Offs Withdrawing Groundwater AdvantagesDisadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Available year- round Sinking of land (subsidence) from overpumping 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 Cheaper to extract than most surface waters Increased cost and contamination from deeper wells
Groundwater Depletion: A Growing Problem The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest). The Ogallala is a non-renewable aquifer. Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. Figure 14-8
Fig. 14-8, p. 314 Groundwater Overdrafts: High Moderate Minor or none
Other Effects of Groundwater Overpumping Groundwater overpumping can cause: land to sink (subsidence), “crushing” the aquifer land to sink (subsidence), “crushing” the aquifer contaminated freshwater aquifers near coastal areas with saltwater. contaminated freshwater aquifers near coastal areas with saltwater. Figure 14-11
Fig. 14-11, p. 315 Major irrigation well Well contaminated with saltwater Water table Fresh groundwater aquifer Sea level Saltwater Interface Seafloor Saltwater intrusion Interface Normal interface EFFECTS OF OVERPUMPING AQUIFERS
Other Effects of Groundwater Overpumping Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater. Figure 14-10
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
Fig. 14-12, p. 316 Solutions Groundwater Depletion PreventionControl Waste less water Raise price of water to discourage waste 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 Do not grow water- intensive crops in dry areas Set and enforce minimum stream flow levels
USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER Large dams and reservoirs can produce cheap electricity produce cheap electricity reduce downstream flooding reduce downstream flooding provide year-round water for irrigating cropland….. provide year-round water for irrigating cropland….. But they also displace people displace people flood terrestrial ecosystems flood terrestrial ecosystems disrupt aquatic systems. disrupt aquatic systems.
Fig. 14-13a, p. 317 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. 14-13b, p. 317 Powerlines Reservoir Dam Powerhouse Intake Turbine
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. 14 major dams and reservoirs, and canals. Water is mostly used in desert area of the U.S. Water is mostly used in desert area of the U.S. Provides electricity from hydroelectric plants for 30 million people (1/10 th of the U.S. population). Provides electricity from hydroelectric plants for 30 million people (1/10 th of the U.S. population).
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 Glen Canyon Dam
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
Fig. 14-14, p. 318 Dam Aqueduct or canal Upper Basin LOWER BASIN 0100 mi. 0150 km Lower Basin UPPER BASIN IDAHO WYOMING Salt Lake City Grand Junction Denver UTAH NEVADA COLORADO Lake Powell Las Vegas Grand Canyon Glen Canyon Dam Boulder City NEW MEXICO ARIZONA Los Angeles Albuquerque Phoenix San Diego Mexicali Yuma Tucson All-American Canal Gulf of California MEXICO CALIFORNIA Palm Springs Colorado River Lake Mead Hoover Dam
How Would You Vote? 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. 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. b. Yes. Dams are critical in providing water and electricity for people, especially in developing countries.
Case Study: China’s Three Gorges Dam on the Yangtze River
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 dam is 2 kilometers long. The electric output is that of 18 large coal- burning or nuclear power plants. The electric output is that of 18 large coal- burning or nuclear power plants. It facilitates ship travel reducing transportation costs. It facilitates ship travel reducing transportation costs. Dam has displaced 1.2 million people, and when filled will displace 5.4 million people Dam has displaced 1.2 million people, and when filled will displace 5.4 million people Dam is built over seismatic fault and already has small cracks. Dam is built over seismatic fault and already has small cracks.
Dam Removal Some dams are being removed for ecological reasons and because they have outlived their usefulness (they tend to fill with silt in an average of about 50 years) 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. 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. The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams. Removing dams can reestablish ecosystems, but can also re-release toxins from sediments into the environment. Removing dams can reestablish ecosystems, but can also re-release toxins from sediments into the environment.
TRANSFERRING WATER FROM ONE PLACE TO ANOTHER Transferring water can make unproductive areas more productive but can cause environmental harm. Pros: Promotes investment, jobs and strong economy. Pros: Promotes investment, jobs and strong economy. Cons: It encourages unsustainable use of water in areas water is not naturally supplied. Cons: It encourages unsustainable use of water in areas water is not naturally supplied.
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
Fig. 14-16, p. 321 CALIFORNIA Sacramento River North Bay Aqueduct Lake Tahoe San Francisco Sacramento South Bay Aqueduct Hoover Dam and Reservoir (Lake Mead) NEVADA UTAH Fresno San Luis Dam and Reservoir Los Angeles Aqueduct Colorado River California Aqueduct Santa Barbara Colorado River Aqueduct Central Arizona Project ARIZONA Los Angeles Salton Sea Phoenix San Diego Tucson MEXICO San Joaquin Valley Feather River Shasta Lake Oroville Dam and Reservoir
Case Study: The Aral Sea Disaster The Aral Sea was once the world’s fourth largest freshwater lake. Figure 14-17
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. 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. 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.
DESALINIZATION OF SEAWATER 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. Distillation: heating saltwater until it evaporates, leaves behind salt in solid form. Reverse osmosis: uses high pressure to force saltwater through a membrane filter. Reverse osmosis: uses high pressure to force saltwater through a membrane filter. Saudi Arabia- 70% of drinking waterSaudi Arabia- 70% of drinking water
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. All three ideas are too expensive All three ideas are too expensive Seeding Clouds leaves chemical residues Seeding Clouds leaves chemical residues
INCREASING WATER SUPPLIES BY WASTING LESS WATER We waste about two-thirds of the water we use worldwide (50% in the US), 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. 65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses. Water is underpriced through government subsidies. Water is underpriced through government subsidies. The lack of government subsidies for improving the efficiency of water use contributes to water waste. The lack of government subsidies for improving the efficiency of water use contributes to water waste.
Fig. 14-18, p. 325 Center pivot Drip irrigation Gravity flow (efficiency 60% and 80% with surge valves) Above- or below- ground pipes or tubes deliver water to individual plant roots. Water usually comes from an aqueduct system or a nearby river. (efficiency 90–95%) (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers.
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. It allows 80% of water to reach crop. Has reduced depletion of Ogallala aquifer in Texas High Plains by 30%. Has reduced depletion of Ogallala aquifer in Texas High Plains by 30%.
Fig. 14-19, p. 326 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
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
Fig. 14-21, p. 327 Solutions Reducing Water Waste Redesign manufacturing processes Repair leaking underground pipes Landscape yards with plants that require little water: “Xeriscaping” Use drip irrigation Fix water leaks Use water meters Raise water prices Use waterless composting toilets Require water conservation in water- short cities Use water-saving toilets, showerheads, and front loading clothes washers Collect and reuse household water (“gray water”) to irrigate lawns and nonedible plants Purify and reuse water for houses, apartments, and office buildings Don't waste energy
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%. 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%. A 10% increase in water prices cuts domestic water use by 3-7%.
How Would You Vote? Should water prices be raised sharply to help reduce water waste? a. No. Poor people, farmers, ranchers, and small businesses would suffer from price increases. a. No. Poor people, farmers, ranchers, and small businesses would suffer from price increases. b. Yes. People would be more likely to conserve water if it is more expensive. b. Yes. People would be more likely to conserve water if it is more expensive.
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 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. Use waterless and odorless composting toilets that convert human fecal matter into a small amount of soil material.
FLOODS: TOO MUCH WATER Comparison of St. Louis, Missouri under normal conditions (1988) and after severe flooding (1993). Figure 14-22
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.
Human activities have contributed to flood deaths and damages. Figure 14-23 These are not “Natural Disasters” !
Fig. 14-23a, p. 330 Oxygen released by vegetation Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Steady river flow Leaf litter improves soil fertility Tree roots stabilize soil and aid water flow Vegetation releases water slowly and reduces flooding Forested Hillside
Fig. 14-23b, p. 330 Tree plantation Roads destabilize hillsides Evapotranspiration decreases Ranching accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Gullies and landslides Heavy rain leaches nutrients from soil and erodes topsoil Silt from erosion blocks rivers and reservoirs and causes flooding downstream Rapid runoff causes flooding After Deforestation
Fig. 14-24, p. 331 Solutions Reducing Flood Damage PreventionControl Preserve forests on watersheds Strengthen and deepen streams (channelization) Preserve and restore wetlands in floodplains Tax all development on floodplains Build levees or floodwalls along streams Use floodplains primarily for -recharging aquifers -sustainable agriculture and forestry -recreation Build dams
SOLUTIONS: USING WATER MORE SUSTAINABLY We can use water more sustainably by cutting waste cutting waste raising water prices raising water prices preserving forests and wetlands in water basins preserving forests and wetlands in water basins slowing population growth. slowing population growth. Figure 14-25
Fig. 14-25, p. 333 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. Eat less beef: 15,000 gallons of water per pound of beef produced. If you use a commercial car wash, try to find one that recycles its water. Xeriscape: 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.
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
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.