2 What would you do Exercise in the future of the Middle east Many analysts list the 3 most serious environmental problems the world facesClimate changeBiodiversity lossEmerging water shortages
3 Core Case Study: Water Conflicts in the Middle East: A Preview of the Future Water shortages in the Middle East: hydrological povertyNile RiverJordan BasinTigris and Euphrates RiversPeacefully solving the problems
5 13-1 Will We Have Enough Usable Water? Concept 13-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.Concept 13-1B One of every six people does not have sufficient access to clean water, and this situation will almost certainly get worse.
6 Freshwater Is an Irreplaceable Resource That We Are Managing Poorly (1) Why is water so important?Earth as a watery world: 71%Freshwater availability: 0.024%Poorly managed resourceHydrologic cycleWater pollution
7 Freshwater Is an Irreplaceable Resource That We Are Managing Poorly (2) Access to water isA global health issueAn economic issueA women’s and children’s issueA national and global security issue
8 Girl Carrying Well Water over Dried Out Earth during a Severe Drought in India
9 Most of the Earth’s Freshwater Is Not Available to Us Hydrologic cycleMovement of water in the seas, land, and airDriven by solar energy and gravityPeople divided intoWater havesWater have-nots
10 Natural Capital: Groundwater System: Unconfined and Confined Aquifer
11 Flowing artesian well Well requiring a pump Water table Unconfined Aquifer Recharge AreaEvaporation and transpirationEvaporationPrecipitationConfined Recharge AreaRunoffFlowing artesian wellWell requiring a pumpStreamFigure 13.3Natural capital: groundwater system. An unconfined aquifer is an aquifer with a permeable water table. A confined aquifer is bounded above and below by less permeable beds of rock, and its water is confined under pressure. Some aquifers are replenished by precipitation; others are not.Water tableInfiltrationLakeInfiltrationUnconfined aquiferLess permeable material such as clayConfined aquiferConfining impermeable rock layerFig. 13-3, p. 316
12 We Get Freshwater from Groundwater and Surface Water (1) Zone of saturationWater tableAquifersNatural rechargeLateral recharge
13 We Get Freshwater from Groundwater and Surface Water (2) Surface runoffWatershed (drainage) basinReliable runoff1/3 of total
14 We Use a Large and Growing Portion of the World’s Reliable Runoff 2/3 of the surface runoff: lost by seasonal floods1/3 runoff usableDomestic: 10%Agriculture: 70%Industrial use: 20%Fred Pearce, author of When the Rivers Run Dry
15 Case Study: Freshwater Resources in the United States More than enough renewable freshwater, unevenly distributed (east vs west)Effect ofFloodsPollutionDrought2007: U.S. Geological Survey projectionWater hotspots
16 Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S.
17 Figure 13.4Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey)Fig. 13-4a, p. 317
18 Average annual precipitation (centimeters) Less than 4181–12241–81More than 122Figure 13.4Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey)Fig. 13-4a, p. 317
19 Figure 13.4Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey)Fig. 13-4b, p. 317
20 Metropolitan regions with population greater than 1 million Figure 13.4Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey)Acute shortageShortageAdequate supplyMetropolitan regions with population greater than 1 millionFig. 13-4b, p. 317
22 Highly likely conflict potential WashingtonNorth DakotaMontanaOregonIdahoSouth DakotaWyomingNevadaNebraskaUtahColoradoKansasCaliforniaOklahomaNew MexicoArizonaFigure 13.5Water hotspots in 17 western states that, by 2025, could face intense conflicts over scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts suggest that this is a map of places not to live during the next 25 years. Question: If you live in one of these hotspot areas, have you noticed any signs of conflict over water supplies? (Data from U.S. Department of the Interior)TexasHighly likely conflict potentialSubstantial conflict potentialModerate conflict potentialUnmet rural water needsFig. 13-5, p. 318
23 Water Shortages Will Grow (1) Dry climateDroughtToo many people using a normal supply of water
24 Water Shortages Will Grow (2) Wasteful use of waterChina and urbanization (2/3rds faced water shortages in 2006)Hydrological poverty
25 Natural Capital Degradation: Stress on the World’s Major River Basins
26 Asia Europe North America Africa South America Australia Stress High Figure 13.6Natural capital degradation: stress on the world’s major river basins, based on a comparison of the amount of water available with the amount used by humans (Concept 13-1B). Questions: If you live in a water-stressed area, what signs of stress have you noticed? In what ways, if any, has it affected your life? (Data from World Commission on Water Use in the 21st Century)StressHighNoneFig. 13-6, p. 319
27 Long-Term Severe Drought Is Increasing CausesExtended period of below-normal rainfallDiminished groundwaterHarmful environmental effectsDries out soilsReduces stream flowsDecreases tree growth and biomassLowers net primary productivity and crop yieldsShift in biomes
28 In Water-Short Areas Farmers and Cities Compete for Water Resources 2007: National Academy of Science studyIncreased corn production in the U.S. to make ethanol as an alternative fuelDecreasing water suppliesAquifer depletionIncrease in pollution of streams and aquifers
29 Who Should Own and Manage Freshwater Resources? (1) Most water resourcesOwned by governmentsManaged as publicly owned resourcesVeolia and Suez: French companiesBuy and manage water resourcesSuccessful outcomes in many areas (china)
30 Who Should Own and Manage Freshwater Resources? (2) Bechtel CorporationPoor water management in BoliviaA subsidiary of Bechtel CorporationPoor water management in EcuadorPotential problems with full privatization of water resourcesFinancial incentive to sell water; not conserve itPoor will still be left out
31 Who should own the water resources? How can more water be produced?
32 In America85% of Americans get their water from publically owned utilitiesWithin 10 years the 2 European companies aim to control 70% of the water supply in the US
33 Assignment: Where do you get your water from? If a company, which one? If your family receives a water bill, ask to see it.Record the following:Amount of water used (in gallons)Period of time recorded amount was used (months)Cost in dollars for that water
34 Pros and Cons for privately owned water companies Companies have money and expertise to manage these resources better (more efficiently) than the governmentCon:Companies motive is money, which may dictate their customer serviceCost of reacquiring water resources is highIncentive is to sell water not conserve itPoor will be left out
35 Exit Questions1) How can some areas that receive a moderate amount of rainfall still suffer from water shortages?2) Between farmers and city dwellers, which group should have greater access to water in water-short areas?3) How might the scarcity of water in the Middle east affect nations that are dependent on oil from the Middle East?
36 What can we do to guarantee our water security?
37 Possible choices for sources of water Extract more GroundwaterBuild More DamsTransfer water from one place to anotherConvert Seawater to FreshwaterReduce the amount of water needed
38 13-2 Is Extracting Groundwater the Answer? Concept Groundwater that is used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.
39 Aquifers Can be renewable resources unless; Water becomes contaminated (salt or pollution)Removed faster than replacedAquifers provide water for nearly ½ the world’s peopleIn US aquifers supplyalmost all drinking water in rural areas1/5th of urban areasabout 40% of irrigation
40 Water Tables Fall When Groundwater Is Withdrawn Faster Than It Is Replenished India, China, and the United StatesThree largest grain producersOverpumping aquifers for irrigation of cropsIndia and ChinaSmall farmers drilling tubewellsEffect on water table (drops, requiring more expensive equip)Saudi ArabiaAquifer depletion and irrigationIrrigated farming will disappear in SA in years
41 Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer
42 What happens to the global food market once cheap groundwater runs out?
43 TRADE-OFFS Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigationAquifer depletion from overpumpingSinking of land (subsidence) from overpumpingAvailable year-roundAquifers polluted for decades or centuriesExists almost everywhereSaltwater intrusion into drinking water supplies near coastal areasRenewable if not overpumped or contaminatedFigure 13.7Advantages and disadvantages of withdrawing groundwater. Question: Which two advantages and which two disadvantages do you think are the most important? Why?Reduced water flows into surface watersNo evaporation lossesIncreased cost and contamination from deeper wellsCheaper to extract than most surface watersFig. 13-7, p. 321
44 Case Study: Aquifer Depletion in the United States Ogallala aquifer: largest known aquiferIrrigates the Great PlainsWater table lowered more than 30mCost of high pumping has eliminated some of the farmersGovernment subsidies to continue farming deplete the aquifer furtherBiodiversity threatened in some areas (loss of wetlands derived from springs)California Central Valley: serious water depletion
45 Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S.
46 Groundwater Overdrafts: Figure 13.9Natural capital degradation: areas of greatest aquifer depletion from groundwater overdraft in the continental United States, including the vast, central Ogallala aquifer. Aquifer depletion is also high in Hawaii and Puerto Rico (not shown on map). See an animation based on this figure at CengageNOW™. Question: If you live in the United States, how is your lifestyle affected directly or indirectly by water withdrawn from the essentially nonrenewable Ogallala aquifer? (Data from U.S. Water Resources Council and U.S. Geological Survey)HighModerateMinor or noneFig. 13-9, p. 322
47 Natural Capital Degradation: The Ogallala is the World’s Largest Known Aquifer
48 SOUTH DAKOTA WYOMING NEBRASKA COLORADO KANSAS OKLAHOMA NEW MEXICO Figure 13.10Natural capital degradation: The Ogallala is the world’s largest known aquifer. If the water in this aquifer were above ground, it could cover all of the lower 48 states with 0.5 meter (1.5 feet) of water. Water withdrawn from this aquifer is used to grow crops, raise cattle, and provide cities and industries with water. As a result, this aquifer, which is renewed very slowly, is being depleted, especially at its thin southern end in parts of Texas, New Mexico, Oklahoma, and Kansas. (Data from U.S. Geological Survey)MilesTEXAS100160KilometersSaturated thickness of Ogallala AquiferLess than 61 meters (200 ft.)61–183 meters (200–600 ft.)More than 183 meters (600 ft.)(as much as 370 meters or 1,200 ft. in places)Fig , p. 323
49 Other effects of ground water pumping Lower water table requires greater cost to farmers to continue to pumpLand subsidence: Take water out, allows land to compact (shrink). Compaction prohibits future rechargeSinkholes: underground cavern collapse after being drained of waterContamination of the groundwater with saltwater. Undrinkable and unusable for irrigation
52 SinkholesNew sinkholes have been correlated to land-use practices, especially from ground-water pumping and from construction and development practices. Sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created. The substantial weight of the new material can trigger an underground collapse of supporting material, thus causing a sinkhole.The overburden sediments that cover buried cavities in the aquifer systems are delicately balanced by ground-water fluid pressure. The water below ground is actually helping to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes In sinkhole-prone areas. If pumping results in a lowering of ground-water levels, then underground structural failure, and thus, sinkholes, can occur.
53 SOLUTIONS Groundwater Depletion Prevention Control Waste less water Raise price of water to discourage wasteSubsidize water conservationTax water pumped from wells near surface watersLimit number of wellsFigure 13.11Ways to prevent or slow groundwater depletion by using water more sustainably. Question: Which two of these solutions do you think are the most important? Why?Set and enforce minimum stream flow levelsDo not grow water-intensive crops in dry areasDivert surface water in wet years to recharge aquifersFig , p. 324
54 Science Focus: Are Deep Aquifers the Answer? Locate the deep aquifers; determine if they contain freshwater or saline waterMajor concernsGeological and ecological impact of pumping water from themFlow beneath more than one countryWho has rights to it?
55 Exit Questions 13-2 List 3 disadvantages to over using groundwater One of the control solutions is to raise the price of water to discourage waste. Do you agree with the solution? What suggestions would you give in order to make this choices more agreeable to the average taxpayer.
56 How much water does your family use a month? Identify source of water used in homeDetermine the amount of water used by month/dayDetermine cost for water Daily/MonthlyWater weights 14 lbs per gallonEstimates?
57 Possible choices for sources of water Extract more GroundwaterBuild More DamsTransfer water from one place to anotherConvert Seawater to FreshwaterReduce the amount of water needed
58 13-3 Is Building More Dams the Answer? Concept 13-3 Building dam and reservoir systems has greatly increased water supplies in some areas, but it has disrupted ecosystems and displaced people.
59 Large Dams and Reservoirs Have Advantages and Disadvantages (1) Main goals of a dam and reservoir systemCapture and store runoffRelease runoff as needed to control:FloodsGenerate electricitySupply irrigation waterRecreation (reservoirs)
60 Large Dams and Reservoirs Have Advantages and Disadvantages (2) Increase the reliable runoff available for farming/drinkingReduce floodingGrow crops in arid regionsRecreation
61 Large Dams and Reservoirs Have Advantages and Disadvantages (3) Displaces peopleFlooded regionsImpaired ecological services of riversLoss of plant and animal speciesFill up with sediment within 50 years
62 Advantages and Disadvantages of Large Dams and Reservoirs
67 The 89-year old, 106-foot high dam, which once helped bring water to residents of Monterey County, is at risk of failing during a significant earthquake or flood. Sediment has been building up behind the dam for years, making it a hazard for those living below it and almost useless as a water storage reservoir. If the dam were to fail, an estimated 2½ million cubic yards of sediment and more than 40 million gallons of water could rush downstream with potentially disastrous consequences.The dam removal will also aid in the recovery of steelhead trout by opening up access to more than 25 square miles of spawning and rearing habitat. Steelhead in Carmel River were listed as threatened under the Endangered Species Act in 1997.“The removal of the San Clemente Dam will help restore richness to the entire ecosystem of the Carmel River while eliminating this major safety threat to the people and their property along it,” said Rodney McInnis, NOAA’s Fisheries Service southwest regional administrator. “The dam removal is vital to the recovery of this important steelhead trout run.”
68 Some Rivers Are Running Dry and Some Lakes Are Shrinking Dams disrupt the hydrologic cycleMajor rivers running dry part of the yearColorado and Rio Grande, U.S.Yangtze and Yellow, ChinaIndus, IndiaDanube, EuropeNile River-Lake Victoria, EgyptLake Chad Africa: disappearing
70 Case Study: The Colorado River Basin— An Overtapped Resource (1) 2,300 km through 7 U.S. states14 Dams and reservoirsLocated in a desert area within the rain shadow of the Rocky MountainsWater supplied mostly from snowmelt of the Rocky Mountains
71 Case Study: The Colorado River Basin— An Overtapped Resource (2) Supplies water and electricity for more than 25 million peopleIrrigation of crops, cheap water from damsRecreation
72 Case Study: The Colorado River Basin— An Overtapped Resource (3) Four Major problemsColorado River basin has very dry landsModest flow of water for its sizeLegal pacts allocated more water for human use than it can supplyAmount of water flowing to the mouth of the river has droppedSilt buildup because of slowing water- filling up the resevoirs
73 Case Study: The Colorado River Basin— An Overtapped Resource (4) What will happen if some of the reservoirs empty out?Economic and ecological catastrophePolitical and legal battles over water
74 What can be done Enact and enforce strict water conservation measures Sharply increase the price of waterSlow population growth/urban developmentStop subsidizing use of water for agriculture in the regionStop building golf courses/green lawns
75 Aerial View of Glen Canyon Dam Across the Colorado River and Lake Powell
76 The Flow of the Colorado River Measured at Its Mouth Has Dropped Sharply
77 Hoover Dam completed (1935) 30Hoover Dam completed (1935)2520Flow (billion cubic meters)15Glen Canyon Dam completed (1963)10Figure 13.16The flow of the Colorado River measured at its mouth has dropped sharply since 1905 as a result of multiple dams, water withdrawals for agriculture and urban areas, and prolonged drought. (Data from U.S. Geological Survey)51910192019301940195019601970198019902000YearFig , p. 328
78 Case Study: China’s Three Gorges Dam (1) World’s largest hydroelectric dam and reservoir2 km long across the Yangtze RiverBenefitsElectricity-producing potential is hugeHolds back the Yangtze River floodwatersAllows cargo-carrying ships
82 Case Study: China’s Three Gorges Dam (2) Harmful effectsDisplaces about 5.4 million peopleBuilt over a seismic faultSignificance?Rotting plant and animal matter producing (Methane) CH4Worse than CO2 emissions as a greenhouse gasWill the Yangtze River become a sewer?
83 Exit questions6) Do the advantages (name some) outweigh the disadvantages (name some) of large dams? 7) List the top 3 measures you would make to deal with the water problems of the Colorado River
84 13-4 Is Transferring Water from One Place to Another the Answer? Concept Transferring water from one place to another has greatly increased water supplies in some areas, but it has also disrupted ecosystems.
85 CA, U.S., Transfers Water from Water-Rich Areas to Water-Poor Areas Water transferred byTunnelsAqueductsUnderground pipesMay cause environmental problemsCalifornia Water Project
86 The California Water Project and the Central Arizona Project
87 Oroville Dam and Reservoir CALIFORNIAShasta LakeNEVADAUTAHSacramento RiverOroville Dam and ReservoirFeather RiverNorth Bay AqueductLake TahoeSacramentoSan FranciscoHoover Dam and Reservoir (Lake Mead)South Bay AqueductFresnoSan Luis Dam and ReservoirSan Joaquin ValleyColorado RiverLos Angeles AqueductCalifornia AqueductARIZONAColorado River AqueductSanta BarbaraFigure 13.17The California Water Project and the Central Arizona Project. These projects involve large-scale water transfers from one watershed to another. Arrows show the general direction of water flow.Central Arizona ProjectLos AngelesPhoenixSalton SeaSan DiegoTucsonMEXICOFig , p. 330
92 Case Study: The Aral Sea Disaster (1) Large-scale water transfers in dry central AsiaWater diverted from riversWetland destruction and wildlife (85%)Fish extinctions and fishing industry collapse
93 Case Study: The Aral Sea Disaster (2) Wind-blown salt (salinization of the land)Farmer’s response to poorer yields…resulting health problemsWater pollution (concentrated, dumped)Climatic changes (thermal buffer, now hotter drier summers)
96 Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake
97 19762006Figure 13.18Natural capital degradation: the Aral Sea was once the world’s fourth largest freshwater lake. Since 1960, it has been shrinking and getting saltier because most of the water from the rivers that replenish it has been diverted to grow cotton and food crops (Concept 13-4). These satellite photos show the sea in 1976 and in It has split into two major parts, little Aral on the left and big Aral on the right. As the lake shrank, it left behind a salty desert, economic ruin, increasing health problems, and severe ecological disruption. Question: What do you think should be done to help prevent further shrinkage of the Aral Sea?Stepped ArtFig a, p. 331
100 Ship Stranded in Desert Formed by Shrinkage of the Aral Sea
101 The threat of anthraxBuried 100’s of metric tons of anthrax spores and other deadly toxins on islandWater level is reduced to point that island is not connected to mainlandRats, fleas could carry disease to humans
102 China Plans a Massive Transfer of Water South-North Water Transfer ProjectWater from three rivers to supply 0.5 billion peopleCompletion in about 2050ImpactEconomicHealthEnvironmental
105 Global Warming its possible effect on the projects
106 Exit questions for 13.4 Water transport Describe the California water projectDescribe the Aral Sea disasterDescribe the proposed China South-North water projectWhat are common benefits of transporting waterWhat are common problems involved with transporting water
107 13-5 Is Converting Salty Seawater to Freshwater the Answer? Concept We can convert salty ocean water to freshwater, but the cost is high, and the resulting salty brine must be disposed of without harming aquatic or terrestrial ecosystems.
108 Removing Salt from Seawater Seems Promising but Is Costly (1) Desalination (2 main methods)DistillationReverse osmosis, microfiltrationAlready used to produce water15,000 plants in 125 countriesSaudi Arabia: highest number (who is 2nd?)Mainly wealthy, energy rich countries
109 Distillation - Boiling Heating separateswater from saltsUse cool incomingwater to condensevapor
114 Benefits Adding usable water to system Huge potential resource Most countries have access to the ocean
115 Removing Salt from Seawater Seems Promising but Is Costly (2) ProblemsHigh cost and energy footprintUse chemicals to keep down algal growth potential to kill many marine organisms, if releasedLarge quantity of chemically contaminated brine( highly concentrated salt water) where do you dispose of it?Water may be too pure, minerals have to me added back into water for it to be useful
116 Science Focus: The Search for Improved Desalination Technology Desalination on offshore ships(what is the advantage?)Solar or wind/wave energyBetter membranesBetter disposal options for the brine wasteReduce water needs, conserve water
117 Exit questions for 13.5 What does desalination mean? What is the difference between the Distillation process and the Reverse Osmosis process?What solutions were presented to overcome the problems associated with desalination?
118 13-6 How Can We Use Water More Sustainably? Concept We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.
119 Reducing Water Waste Has Many Benefits (1) We have the potential the impending global water shortage just by not wasting (conserving) water we already use.Water conservationImproves irrigation efficiencyImproves collection efficiencyUses less in homes and businesses
120 Reducing Water Waste Has Many Benefits (2) Worldwide: 65–70% lossTwo largest sources of waste:Evaporation, leaksBig reason for wasteWater prices: low cost to userGovernment subsidies: more needed? What should government support with your money?
121 We Can Cut Water Waste in Irrigation Flood irrigationWastefulCenter pivot, low pressure sprinklersLow-energy, precision application sprinklersDrip or trickle irrigation, micro-irrigationCostly; less water waste
125 (efficiency 60% and 80% with surge valves) Figure 13.20Major irrigation systems. Because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new, low-cost, drip-irrigation systems may change this situation.Center pivot(efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler)Drip irrigation(efficiency 90–95%)Gravity flow(efficiency 60% and 80% with surge valves)Above- or below-ground pipes or tubes deliver water to individual plant roots.Water usually pumped from underground and sprayed from mobile boom with sprinklers.Water usually comes from an aqueduct system or a nearby river.Fig , p. 335
128 (efficiency 60% and 80% with surge valves) Center pivot(efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler)Water usually pumped from underground and sprayed from mobile boom with sprinklers.Drip irrigation(efficiency 90–95%)Above- or below-ground pipes or tubes deliver water to individual plant roots.Gravity flow(efficiency 60% and 80% with surge valves)Water usually comes from an aqueduct system or a nearby river.Figure 13.20Major irrigation systems. Because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new, low-cost, drip-irrigation systems may change this situation.Stepped ArtFig , p. 335
136 We Can Use Less Water to Remove Wastes Can we mimic how nature deals with waste?Waterless composting toilets
137 We Need to Use Water More Sustainably “The frog does not drink up the pond in which it lives”Blue revolutionWhat can cities, industries, governments do to reduce water consumption?
138 SOLUTIONS Sustainable Water Use Waste less water and subsidize water conservationDo not deplete aquifersPreserve water qualityProtect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release waterFigure 13.23Methods for achieving more sustainable use of the earth’s water resources (Concept 13-6). Question: Which two of these solutions do you think are the most important? Why?Get agreements among regions and countries sharing surface water resourcesRaise water pricesSlow population growthFig , p. 337
141 Why do you think people do not conserve water?
142 Reasons Takes time Costs more money than doing nothing Benefit is not immediate
143 Exit questions 13.6What actions can you take to reduce the amount of water that you consume?What methods of irrigation use the least amount of water? Which method could you use in your own garden?Name 3 important solutions in reducing water waste in cities.
144 13-7 How Can We Reduce the Threat of Flooding? Concept We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds and by not building in areas subject to frequent flooding.
145 Some Areas Get Too Much Water from Flooding (1) Flood plainsHighly productive wetlandsProvide natural flood and erosion controlMaintain high water qualityRecharge groundwaterBenefits of floodplainsFertile soilsNearby rivers for use and recreationFlatlands for urbanization and farming
146 Some Areas Get Too Much Water from Flooding (2) Dangers of floodplains and floodsDeadly and destructiveHuman activities worsen floodsFailing dams and water diversionHurricane Katrina and the Gulf CoastRemoval of coastal wetlands
147 Natural Capital Degradation: Hillside Before and After Deforestation
148 Forested Hillside Oxygen released by vegetation Diverse ecological habitatEvapotranspirationTrees reduce soil erosion from heavy rain and windAgricultural landFigure 13.25Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber, fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding and pollution in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.” See an animation based on this figure at CengageNOW. Question: How might a drought in this area make these effects even worse?Tree roots stabilize soilVegetation releases water slowly and reduces floodingForested HillsideFig a, p. 339
149 After Deforestation Tree plantation Evapotranspiration decreases Roads destabilize hillsidesOvergrazing accelerates soil erosion by water and windWinds remove fragile topsoilAgricultural land is flooded and silted upGullies and landslidesFigure 13.25Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber, fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding and pollution in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.” See an animation based on this figure at CengageNOW. Question: How might a drought in this area make these effects even worse?Heavy rain erodes topsoilSilt from erosion fills rivers and reservoirsRapid runoff causes floodingAfter DeforestationFig b, p. 339
150 Forested Hillside After Deforestation Oxygen released by vegetation Diverse ecological habitatEvapotranspirationTrees reduce soil erosion from heavy rain and windTree roots stabilize soilVegetation releases water slowly and reduces floodingForested HillsideAgricultural landStepped ArtTree plantationRoads destabilize hillsidesOvergrazing accelerates soil erosion by water and windWinds remove fragile topsoilAgricultural land is flooded and silted upGullies and landslidesHeavy rain erodes topsoilSilt from erosion fills rivers and reservoirsRapid runoff causes floodingAfter DeforestationEvapotranspiration decreasesFigure 13.25Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber, fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding and pollution in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.” See an animation based on this figure at CengageNOW. Question: How might a drought in this area make these effects even worse?Fig a, p. 339
151 Case Study: Living Dangerously on Floodplains in Bangladesh Dense populationLocated on coastal floodplainModerate floods maintain fertile soilIncreased frequency of large floodsEffects of development in the Himalayan foothillsDestruction of coastal wetlands
152 We Can Reduce Flood Risks Rely more on nature’s systemsWetlandsNatural vegetation in watershedsRely less on engineering devicesDamsLevees
154 SOLUTIONS Reducing Flood Damage Prevention Control Preserve forests on watershedsStraighten and deepen streams (channelization)Preserve and restore wetlands in floodplainsBuild levees or floodwalls along streamsTax development on floodplainsFigure 13.26Methods for reducing the harmful effects of flooding (Concept 13-7). Question: Which two of these solutions do you think are the most important? Why?Use floodplains primarily for recharging aquifers, sustainable agriculture and forestryBuild damsFig , p. 340