3.6 Water Resources

Water, water everywhere and not a drop to drink! 3.6 Water Resources

Connections between water resources and food resourcesEarths water budgetOnly about 3% of the water on our planet is fresh water (97% salt water)69% of fresh water is in polar ice caps and glaciers 30% is ground waterThe remaining 1% is lakes rivers swamps and in the atmosphere

Turnover timeTime it takes water to enter and leave a part of a systemWater in oceans= 37000 yearsWater is icecaps= 16000 yearsWater in ground= 300 yearsWater in atmosphere = 9 daysWater in rivers = 12-20 daysOceanic Conveyer belt

Human Uses for Fresh water

Domestic water ( drinking, washing, cleaning)IrrigationIndustry (manufacturing, mining, andagriculture)Hydroelectric powerTransportation (ships on lakes/rivers)Boundaries (states and nations)

Water Usage Pie Chart

Virtual Water Use

Figure 13.A: Producing and delivering a single one of each of the products shown here requires the equivalent of at least one and usually many bathtubs full of water, called virtual water. A typical bathtub contains about 151 liters (40 gallons) of water. The average amount of water used to raise a single steer during its typical 3-year life from birth to slaughter and to market by an industrial producer would fill more than 20,000 bathtubs. This includes water used for providing the steer with food and drinking water and water used to clean up its wastes. It is not surprising that about 70% of the worlds water is used for irrigation, because it takes about 1,000 metric tons (900 tons) of water to produce 1 metric ton (0.9 ton) of grain. (Data from UNESCO-IHE Institute for Water Education, UN Food and Agriculture Organization, World Water Council, Water Footprint Network, and Coca Cola Company) [Photos from Shutterstock; Credits (top to bottom: Kirsty Pargeter, Aleksandra Nadeina, Alexander Kallina, Kelpfish, Wolfgang Amri, Skip Odonnell, Eky Chan, Rafal Olechowski)]9Problems related to freshwater useLow water levels in rivers, streams and lakesSlow water flowUnderground aquifers become exhausted Irrigation causes much of the water to evaporate before it can be used. Fertilizer and pesticides and industries pollute streams Industries release warm water into rivers, causes dissolved oxygen to decrease (warm water contains less Oxygen). SolutionsReduce domestic use of fresh water (shorter showers/wash cars less)Irrigation: Drought resistant crops- Closed pipes instead of open canalsReduce farming contamination (pesticides and fertilizers). Force industry to remove pollutants from wastewater

Case Study: The Colorado River: An Over tapped Resource1,429 miles through 7 U.S. statesSupplies water and electricity ~30 million people in USA and MexicoHeavily dammed for electricity and agriculture (14 dams)80% used for irrigation and cattle ranchingDownstream (in Mexico) can dry up completely some years and lead to droughts.Salinity problems prevent irrigation in MexicoDried river causes loss of biodiversity

12The Colorado River BasinFig. 13-1, p. 317

Figure 13.1: 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. Two large reservoirsLake Mead behind the Hoover Dam and Lake Powell behind the Glen Canyon Damstore about 80% of the water in this basin.13Aerial View of Glen Canyon Dam Across the Colorado River and Lake Powell

Fig. 13-2, p. 317Figure 13.2: The Glen Canyon Dam across the Colorado River was completed in 1963. Lake Powell behind the dam is the second largest reservoir in the United States.14A Closer Look at the Over tapped Colorado River BasinCurrent rate of river withdrawal is not sustainableMuch water used for agriculture that is inefficient with water use: cotton, alfalfa, riceWater use subsidized by governmentReservoirsLeak water into ground belowLose much water through evaporationFill up with silt load of river, depriving deltaCould eventually lose ability to store water and create electricityStates must conserve water, control population, and slow urban development

Water Shortages Will GrowDry climatesDroughtToo many people using a normal supply of waterWasteful use of water30% earths land area experiences severe droughtPotential conflicts/wars over waterRefugees from arid landsIncreased mortality

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Fig. 13-5, p. 322WashingtonOregonMontanaNorth DakotaIdahoSouth DakotaWyomingNevadaNebraskaUtahColoradoKansasCaliforniaOklahomaArizonaNew MexicoTexasHighly likely conflict potentialSubstantial conflict potentialModerate conflict potentialUnmet rural water needsFigure 13.5: This map shows water scarcity 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 in the foreseeable future. Question: Which, if any, of these areas are found in the Colorado River basin (Figure 13-1)? (Data from U.S. Department of the Interior)Natural Capital Degradation: Stress on the Worlds Major River Basins

Fig. 13-6, p. 323Figure 13.6: Natural capital degradation. The worlds major river basins differ in their degree of water scarcity stress, the measurement of which is 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)18Is Extracting Groundwater the Answer? Groundwater is Being Withdrawn Faster Than It Is ReplenishedMost aquifers are renewableAquifers provide drinking water for half the worldWater tables are falling in many parts of the world, primarily from crop irrigation

Water: A Replenishable ResourceIndia, China, and the United StatesThree largest grain producersOver pumping aquifers for irrigation of cropsSmall farmers drilling tube wells Effect on water tableSaudi ArabiaAquifer depletion and irrigation

20Fig. 13-7, p. 325Trade-OffsWithdrawing GroundwaterAdvantagesDisadvantagesUseful for drinking and irrigationAquifer depletion from overpumpingExists almost everywhereSinking of land from over pumpingRenewable if not overpumped or contaminatedPollution of aquifers lasts decades or centuriesDeeper wells are nonrenewableCheaper to extract than most surface waters

Figure 13.7: Withdrawing groundwater from aquifers has advantages and disadvantages. Questions: Which two advantages and which two disadvantages do you think are the most important? Why?

Is Building More Dams the Answer? Main goal of a dam and reservoir systemCapture and store runoffRelease runoff as needed to control:FloodsGenerate electricitySupply irrigation waterRecreation (reservoirs)

22Advantages and Disadvantages of DamsAdvantagesReduce floodingZero emissions electricity production

DisadvantagesDisplaces people with reservoir Impaired ecological services of riversLoss of plant and animal speciesCan cause other streams and lakes to dry up

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Fig. 13-13a, p. 328Provides irrigation water above and below damFlooded land destroys forests or cropland and displaces peopleLarge losses of water through evaporationProvides water for drinkingDeprives downstream cropland and estuaries of nutrient-rich siltReservoir useful for recreation and fishingRisk of failure and devastating downstream oodingCan produce cheap electricity (hydropower)Reduces down-stream flooding of cities and farmsDisrupts migration and spawning of some fishFigure 13.13: Trade-offs. Large dams and reservoirs have advantages (green) and disadvantages (orange) (Concept 13-3). The worlds 45,000 large dams (15 meters (49 feet) or higher) capture and store about 14% of the worlds surface runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used in 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the countrys entire river flow. Question: Which single advantage and which single disadvantage do you think are the most important?

Fig. 13-13b, p. 328PowerlinesReservoirDamIntakePowerhouseTurbineFigure 13.13: Trade-offs. Large dams and reservoirs have advantages (green) and disadvantages (orange) (Concept 13-3). The worlds 45,000 large dams (15 meters (49 feet) or higher) capture and store about 14% of the worlds surface runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used in 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the countrys entire river flow. Question: Which single advantage and which single disadvantage do you think are the most important?Is irrigation the answer? Case Study: The Aral Sea DisasterLarge-scale water transfers for irrigation stops flow of water into the Aral SeaLess Water = Increase in salinityFish population declinesWater pollutionRestoration effortsMore efficient irrigationDam built to help raise lake level

26Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake

Fig. 13-17, p. 332

Figure 13.17: Natural capital degradation. The Aral Sea was one of the worlds largest saline lakes. Since 1960, it has been shrinking and getting saltier because most of the water from the two rivers that replenish it has been diverted to grow cotton and food crops. These satellite photos show the sea in 1976 and in 2009. As the Southern Aral Sea shrank, it split into two lakes and left behind a salty desert, economic ruin, increasing health problems, and severe ecological disruption. By late 2009, the larger eastern part of the once huge Southern Aral Sea was gone (bottom-right part of each photo). The smaller Northern Aral Sea (top of each photo) has also shrunk, but not nearly as much as the Southern Aral Sea has. Question: What are three things that you think should be done to help prevent further shrinkage of the Aral Sea?27Is Desalination the Answer? Desalination- Removing Salt from Seawater Distillation: evaporate water, leaving salts behindReverse osmosis, microfiltration: use high pressure to remove saltsProblems: Very Costly, Kills Organisms, Creates Briny Wastewater14,450 plants in 125 countriesSaudi Arabia: highest number

28The Search for Improved Desalination TechnologyDesalination on offshore shipsSolar or wind energyUse ocean waves for powerBuild desalination plants near electric power plants

29Deforestation Above Chinas Yangtze River Contribute to Erosion and Floods

Fig. 13-26, p. 341Figure 13.26: Deforestation of hills and mountains in Chinas Yangtze River Basin contributed to increased flooding, topsoil erosion, and the flow of eroded sediment into the Yangtze River. Because of these harmful effects, China stopped the deforestation and established a massive tree-planting program to reforest the degraded land.30

Fig. 13-25a, p. 340Diverse ecological habitatEvapotranspirationTrees reduce soil erosion from heavy rain and windAgricultural landTree roots stabilize soilVegetation releases water slowly and reduces floodingForested HillsideFigure 13.25: Natural capital degradation. These diagrams show a 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. 13-25b, p. 340Tree plantationRoads destabilize hillsidesOvergrazing accelerates soil erosion by water and windEvapotranspiration decreasesWinds remove fragile topsoilAgricultural land is flooded and silted upGullies and landslidesHeavy rain erodes topsoilSilt from erosion fills rivers and reservoirsRapid runoff causes floodingAfter DeforestationFigure 13.25: Natural capital degradation. These diagrams show a 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?Three Big IdeasOne of the worlds major environmental problems is the growing shortage of freshwater in many parts of the world.We can increase water supplies in water-short areas in a number of ways, but the most important way is to reduce overall water use and waste by using water more sustainably.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.